diff --git a/src/CounterVector.cc b/src/CounterVector.cc
index 8ed4c30427..a661492313 100644
--- a/src/CounterVector.cc
+++ b/src/CounterVector.cc
@@ -1,5 +1,6 @@
 #include "CounterVector.h"
 
+#include <limits>
 #include "BitVector.h"
 #include "Serializer.h"
 
@@ -15,23 +16,66 @@ CounterVector::~CounterVector()
 
 bool CounterVector::Increment(size_type cell, count_type value)
   {
-  // TODO
-  assert(! "not yet implemented");
+  assert(cell < Size());
+  assert(value != 0);
+  size_t lsb = cell * width_;
+  if (value >= Max())
+  {
+    bool r = false;
+    for (size_t i = 0; i < width_; ++i)
+      if (! (*bits_)[lsb + i])
+      {
+        bits_->Set(lsb + i);
+        if (! r)
+          r = true;
+      }
+    return r;
+  }
+  bool carry = false;
+  for (size_t i = 0; i < width_; ++i)
+  {
+    bool b1 = (*bits_)[lsb + i];
+    bool b2 = value & (1 << i);
+    (*bits_)[lsb + i] ^= b2 != carry; // bit1 ^ bit2 ^ carry
+    carry = carry ? b1 || b2 : b1 && b2;
+  }
+  if (! carry)
+    return true;
+  for (size_t i = 0; i < width_; ++i)
+    bits_->Set(lsb + i);
   return false;
   }
 
 bool CounterVector::Decrement(size_type cell, count_type value)
   {
-  // TODO
-  assert(! "not yet implemented");
-  return false;
+  assert(cell < Size());
+  size_t lsb = cell * width_;
+  bool success;
+  while (value --> 0)
+    {
+    success = false;
+    for (size_t i = lsb; i < lsb + width_; ++i)
+      if ((*bits_)[i])
+        {
+        bits_->Reset(i);
+        while (i && i > lsb)
+          bits_->Set(--i);
+        success = true;
+        break;
+        }
+    }
+  return success;
   }
 
 CounterVector::count_type CounterVector::Count(size_type cell) const
   {
-  // TODO
-  assert(! "not yet implemented");
-  return 0;
+  assert(cell < Size());
+  size_t cnt = 0, order = 1;
+  size_t lsb = cell * width_;
+  for (size_t i = lsb; i < lsb + width_; ++i, order <<= 1)
+    if ((*bits_)[i])
+      cnt |= order;
+  return cnt;
   }
 
 CounterVector::size_type CounterVector::Size() const
@@ -39,6 +83,12 @@ CounterVector::size_type CounterVector::Size() const
   return bits_->Blocks() / width_;
   }
 
+size_t CounterVector::Max() const
+  {
+  return std::numeric_limits<size_t>::max()
+    >> (std::numeric_limits<size_t>::digits - width_);
+  }
+
 bool CounterVector::Serialize(SerialInfo* info) const
   {
   return SerialObj::Serialize(info);
diff --git a/src/CounterVector.h b/src/CounterVector.h
index ecc8fe90e0..868beaca9b 100644
--- a/src/CounterVector.h
+++ b/src/CounterVector.h
@@ -19,6 +19,8 @@ public:
    * @param width The number of bits that each cell occupies.
    *
    * @param cells The number of cells in the bitvector.
+   *
+   * @pre `cells > 0 && width > 0`
    */
   CounterVector(size_t width, size_t cells = 1024);
 
@@ -32,6 +34,8 @@ public:
    * @param value The value to add to the current counter in *cell*.
    *
    * @return `true` if adding *value* to the counter in *cell* succeeded.
+   *
+   * @pre `cell < Size()`
    */
   bool Increment(size_type cell, count_type value);
 
@@ -43,6 +47,8 @@ public:
    * @param value The value to subtract from the current counter in *cell*.
    *
    * @return `true` if subtracting *value* from the counter in *cell* succeeded.
+   *
+   * @pre `cell < Size()`
    */
   bool Decrement(size_type cell, count_type value);
 
@@ -52,6 +58,8 @@ public:
    * @param cell The cell index to retrieve the count for.
    *
    * @return The counter associated with *cell*.
+   *
+   * @pre `cell < Size()`
    */
   count_type Count(size_type cell) const;
 
@@ -62,6 +70,13 @@ public:
    */
   size_type Size() const;
 
+  /**
+   * Computes the maximum counter value.
+   *
+   * @return The maximum counter value based on the width.
+   */
+  size_t Max() const;
+
   bool Serialize(SerialInfo* info) const;
   static CounterVector* Unserialize(UnserialInfo* info);