diff --git a/cpp/nucleotide-count/nucleotide_count.cpp b/cpp/nucleotide-count/nucleotide_count.cpp
new file mode 100644
index 0000000..fea82c4
--- /dev/null
+++ b/cpp/nucleotide-count/nucleotide_count.cpp
@@ -0,0 +1,46 @@
+#include "nucleotide_count.h"
+
+#include <stdexcept>
+#include <unordered_set>
+
+
+namespace dna {
+
+using namespace std;
+
+
+static const unordered_set<char> valid_nucleotides = {'A', 'T', 'C', 'G'};
+
+static inline bool is_valid_nucleotide(char c)
+{
+    return valid_nucleotides.find(c) != valid_nucleotides.cend();
+}
+
+counter::counter(const string &str)
+{
+    for (auto c : valid_nucleotides)
+        nucleotide_counts_[c] = 0;
+
+    for (auto c : str) {
+
+        if (!is_valid_nucleotide(c))
+            throw invalid_argument("invalid sequence");
+
+        ++nucleotide_counts_[c];
+    }
+}
+
+NucleotideCounts counter::nucleotide_counts() const
+{
+    return nucleotide_counts_;
+}
+
+int counter::count(char c) const
+{
+    if (!is_valid_nucleotide(c))
+        throw invalid_argument("invalid nucleotide");
+
+    return nucleotide_counts_.at(c);
+}
+
+}
diff --git a/cpp/nucleotide-count/nucleotide_count.h b/cpp/nucleotide-count/nucleotide_count.h
new file mode 100644
index 0000000..9017300
--- /dev/null
+++ b/cpp/nucleotide-count/nucleotide_count.h
@@ -0,0 +1,24 @@
+#pragma once
+
+#define EXERCISM_RUN_ALL_TESTS
+
+#include <map>
+#include <string>
+
+
+namespace dna {
+
+typedef std::map<char, int> NucleotideCounts;
+
+class counter
+{
+    NucleotideCounts nucleotide_counts_;
+
+public:
+
+    counter(const std::string &str);
+    NucleotideCounts nucleotide_counts() const;
+    int count(char c) const;
+};
+
+}