Very recently nitric oxide (NO) was considered a highly toxic gas until its crucial function in humans was discovered. Its emergence as a biological messenger in the cardiovascular, nervous and immune systems has prompted immense interest. The multiple roles and diversity of NO in physiology make it an attractive therapeutic alternative for a wide range of diseases. This has led to current interest in designing storage and delivery materials. Here we report the use of metal exchanged zeolites as an alternative storage and delivery device for NO in human physiology.