diff --git a/src/client/pv/monitor.h b/src/client/pv/monitor.h
new file mode 100644
index 0000000..54ac1d1
--- /dev/null
+++ b/src/client/pv/monitor.h
@@ -0,0 +1,128 @@
+/* monitor.h */
+/*
+ * Copyright information and license terms for this software can be
+ * found in the file LICENSE that is included with the distribution
+ */
+/**
+ *  @author mrk
+ */
+#ifndef MONITOR_H
+#define MONITOR_H
+
+#include <pv/status.h>
+#include <pv/destroyable.h>
+#include <pv/pvData.h>
+#include <pv/sharedPtr.h>
+#include <pv/bitSet.h>
+#include <pv/requester.h>
+
+#include <shareLib.h>
+
+namespace epics { namespace pvData { 
+
+class MonitorElement;
+typedef std::tr1::shared_ptr<MonitorElement> MonitorElementPtr;
+typedef std::vector<MonitorElementPtr> MonitorElementPtrArray;
+
+class Monitor;
+typedef std::tr1::shared_ptr<Monitor> MonitorPtr;
+
+
+/**
+ * @brief An element for a monitorQueue.
+ *
+ * Class instance representing monitor element.
+ * @author mrk
+ */
+class epicsShareClass MonitorElement {
+    public:
+    POINTER_DEFINITIONS(MonitorElement);
+    MonitorElement(){}
+    MonitorElement(PVStructurePtr const & pvStructurePtr)
+    : pvStructurePtr(pvStructurePtr),
+      changedBitSet(BitSet::create(static_cast<uint32>(pvStructurePtr->getNumberFields()))),
+      overrunBitSet(BitSet::create(static_cast<uint32>(pvStructurePtr->getNumberFields())))
+    {}
+    PVStructurePtr pvStructurePtr;
+    BitSet::shared_pointer changedBitSet;
+    BitSet::shared_pointer overrunBitSet;
+};
+
+/**
+ * @brief Monitor changes to fields of a pvStructure.
+ *
+ * This is used by pvAccess to implement monitors.
+ * @author mrk
+ */
+class epicsShareClass Monitor : public Destroyable{
+    public:
+    POINTER_DEFINITIONS(Monitor);
+    virtual ~Monitor(){}
+    /**
+     * Start monitoring.
+     * @return completion status.
+     */
+    virtual Status start() = 0;
+    /**
+     * Stop Monitoring.
+     * @return completion status.
+     */
+    virtual Status stop() = 0;
+    /**
+     * If monitor has occurred return data.
+     * @return monitorElement for modified data.
+     * Must call get to determine if data is available.
+     */
+    virtual MonitorElementPtr poll() = 0;
+    /**
+     * Release a MonitorElement that was returned by poll.
+     * A poll() must be called after the release() to check the presence of any modified data.
+     * @param monitorElement
+     */
+    virtual void release(MonitorElementPtr const & monitorElement) = 0;
+
+    struct Stats {
+        size_t nfilled; //!< # of elements ready to be poll()d
+        size_t noutstanding; //!< # of elements poll()d but not released()d
+        size_t nempty; //!< # of elements available for new remote data
+    };
+
+    virtual void getStats(Stats& s) const {
+        s.nfilled = s.noutstanding = s.nempty = 0;
+    }
+};
+
+
+/**
+ * @brief Callback implemented by monitor clients.
+ *
+ * Requester for ChannelMonitor.
+ * @author mrk
+ */
+class epicsShareClass MonitorRequester : public virtual Requester {
+    public:
+    POINTER_DEFINITIONS(MonitorRequester);
+    virtual ~MonitorRequester(){}
+    /**
+     * The client and server have both completed the createMonitor request.
+     * @param status Completion status.
+     * @param monitor The monitor
+     * @param structure The structure defining the data.
+     */
+    virtual void monitorConnect(Status const & status,
+        MonitorPtr const & monitor, StructureConstPtr const & structure) = 0;
+    /**
+     * A monitor event has occurred.
+     * The requester must call Monitor.poll to get data.
+     * @param monitor The monitor.
+     */
+    virtual void monitorEvent(MonitorPtr const & monitor) = 0;
+    /**
+     * The data source is no longer available.
+     * @param monitor The monitor.
+     */
+    virtual void unlisten(MonitorPtr const & monitor) = 0;
+};
+
+}}
+#endif  /* MONITOR_H */