diff --git a/prometheus/counter_test.go b/prometheus/counter_test.go
index 8d5cd0b..0b79728 100644
--- a/prometheus/counter_test.go
+++ b/prometheus/counter_test.go
@@ -28,11 +28,25 @@ func TestCounterAdd(t *testing.T) {
 		ConstLabels: Labels{"a": "1", "b": "2"},
 	}).(*counter)
 	counter.Inc()
-	if expected, got := 1., math.Float64frombits(counter.valBits); expected != got {
+	if expected, got := 0.0, math.Float64frombits(counter.valBits); expected != got {
+		t.Errorf("Expected %f, got %f.", expected, got)
+	}
+	if expected, got := int64(1), counter.valInt; expected != got {
 		t.Errorf("Expected %f, got %f.", expected, got)
 	}
 	counter.Add(42)
-	if expected, got := 43., math.Float64frombits(counter.valBits); expected != got {
+	if expected, got := 0.0, math.Float64frombits(counter.valBits); expected != got {
+		t.Errorf("Expected %f, got %f.", expected, got)
+	}
+	if expected, got := int64(43), counter.valInt; expected != got {
+		t.Errorf("Expected %f, got %f.", expected, got)
+	}
+
+	counter.Add(24.42)
+	if expected, got := 24.42, math.Float64frombits(counter.valBits); expected != got {
+		t.Errorf("Expected %f, got %f.", expected, got)
+	}
+	if expected, got := int64(43), counter.valInt; expected != got {
 		t.Errorf("Expected %f, got %f.", expected, got)
 	}
 
@@ -43,7 +57,7 @@ func TestCounterAdd(t *testing.T) {
 	m := &dto.Metric{}
 	counter.Write(m)
 
-	if expected, got := `label:<name:"a" value:"1" > label:<name:"b" value:"2" > counter:<value:43 > `, m.String(); expected != got {
+	if expected, got := `label:<name:"a" value:"1" > label:<name:"b" value:"2" > counter:<value:67.42 > `, m.String(); expected != got {
 		t.Errorf("expected %q, got %q", expected, got)
 	}
 }
@@ -112,3 +126,87 @@ func expectPanic(t *testing.T, op func(), errorMsg string) {
 
 	op()
 }
+
+func TestCounterAddInf(t *testing.T) {
+	counter := NewCounter(CounterOpts{
+		Name: "test",
+		Help: "test help",
+	}).(*counter)
+
+	counter.Inc()
+	if expected, got := 0.0, math.Float64frombits(counter.valBits); expected != got {
+		t.Errorf("Expected %f, got %f.", expected, got)
+	}
+	if expected, got := int64(1), counter.valInt; expected != got {
+		t.Errorf("Expected %f, got %f.", expected, got)
+	}
+
+	counter.Add(math.Inf(1))
+	if expected, got := math.Inf(1), math.Float64frombits(counter.valBits); expected != got {
+		t.Errorf("valBits expected %f, got %f.", expected, got)
+	}
+	if expected, got := int64(1), counter.valInt; expected != got {
+		t.Errorf("valInts expected %d, got %d.", expected, got)
+	}
+
+	counter.Inc()
+	if expected, got := math.Inf(1), math.Float64frombits(counter.valBits); expected != got {
+		t.Errorf("Expected %f, got %f.", expected, got)
+	}
+	if expected, got := int64(2), counter.valInt; expected != got {
+		t.Errorf("Expected %d, got %d.", expected, got)
+	}
+
+	m := &dto.Metric{}
+	counter.Write(m)
+
+	if expected, got := `counter:<value:inf > `, m.String(); expected != got {
+		t.Errorf("expected %q, got %q", expected, got)
+	}
+}
+
+func TestCounterAddLarge(t *testing.T) {
+	counter := NewCounter(CounterOpts{
+		Name: "test",
+		Help: "test help",
+	}).(*counter)
+
+	// large overflows the underlying type and should therefore be stored in valBits
+	large := float64(math.MaxInt64 + 1)
+	counter.Add(large)
+	if expected, got := large, math.Float64frombits(counter.valBits); expected != got {
+		t.Errorf("valBits expected %f, got %f.", expected, got)
+	}
+	if expected, got := int64(0), counter.valInt; expected != got {
+		t.Errorf("valInts expected %d, got %d.", expected, got)
+	}
+
+	m := &dto.Metric{}
+	counter.Write(m)
+
+	if expected, got := fmt.Sprintf("counter:<value:%0.15e > ", large), m.String(); expected != got {
+		t.Errorf("expected %q, got %q", expected, got)
+	}
+}
+
+func TestCounterAddSmall(t *testing.T) {
+	counter := NewCounter(CounterOpts{
+		Name: "test",
+		Help: "test help",
+	}).(*counter)
+	small := 0.000000000001
+	counter.Add(small)
+	if expected, got := small, math.Float64frombits(counter.valBits); expected != got {
+		t.Errorf("valBits expected %f, got %f.", expected, got)
+	}
+	if expected, got := int64(0), counter.valInt; expected != got {
+		t.Errorf("valInts expected %d, got %d.", expected, got)
+	}
+
+	m := &dto.Metric{}
+	counter.Write(m)
+
+	if expected, got := fmt.Sprintf("counter:<value:%0.0e > ", small), m.String(); expected != got {
+		t.Errorf("expected %q, got %q", expected, got)
+	}
+}
diff --git a/prometheus/value.go b/prometheus/value.go
index 4a9cca6..5626e80 100644
--- a/prometheus/value.go
+++ b/prometheus/value.go
@@ -45,6 +45,8 @@ type value struct {
 	// to go first in the struct to guarantee alignment for atomic
 	// operations.  http://golang.org/pkg/sync/atomic/#pkg-note-BUG
 	valBits uint64
+	// valInt is used to store values that are exact integers
+	valInt int64
 
 	selfCollector
 
@@ -82,15 +84,26 @@ func (v *value) SetToCurrentTime() {
 	v.Set(float64(time.Now().UnixNano()) / 1e9)
 }
 
+// add adjusts the underlying int64
+func (v *value) add(delta int64) {
+	atomic.AddInt64(&v.valInt, delta)
+}
+
 func (v *value) Inc() {
-	v.Add(1)
+	v.add(1)
 }
 
 func (v *value) Dec() {
-	v.Add(-1)
+	v.add(-1)
 }
 
 func (v *value) Add(val float64) {
+	ival := int64(val)
+	if float64(ival) == val {
+		v.add(ival)
+		return
+	}
+
 	for {
 		oldBits := atomic.LoadUint64(&v.valBits)
 		newBits := math.Float64bits(math.Float64frombits(oldBits) + val)
@@ -105,7 +118,10 @@ func (v *value) Sub(val float64) {
 }
 
 func (v *value) Write(out *dto.Metric) error {
-	val := math.Float64frombits(atomic.LoadUint64(&v.valBits))
+	fval := math.Float64frombits(atomic.LoadUint64(&v.valBits))
+	ival := atomic.LoadInt64(&v.valInt)
+	val := fval + float64(ival)
+
 	return populateMetric(v.valType, val, v.labelPairs, out)
 }