1500 accelerated thermal cycle tests have been conducted to study the changes in latent heat of fusion and melting temperature of commercial grade acetamide, stearic acid and paraffin wax. It has been noticed that the stearic acid melts over a wide range of temperature. has shown two melting points and has large variations in latent heat of fusion. Paraffin wax and acetamide have shown reasonably good thermal stability for melting temperature and variations in latent heat of fusion during the cycling process.