The effects of the commercial thermal processing and storage on the retention of ascorbic acid, thiamine and riboflavin in potatoes and cow peas have been studied. Samples have been collected after washing, blanching and thermal processing operations. Washing had no significant effect on the levels of these vitamins in both potatoes and cow peas. Either blanching (at 100 degrees C for 2 min) or thermal processing (at 121 degrees C for 20 min) had a great effect on the retention of ascorbic acid, thiamine and riboflavin. While the retention of ascorbic acid and thiamine had been affected by the storage conditions (at 25 degrees C for 6 month), there was no significant change of riboflavin content in potatoes and cow peas. Based on a laboratory study, leaching was largely responsible for losses of these vitamins during water blanching, thermal processing and storage.