Ascorbic acid (vitamin C) has been widely used in cosmetics and dermatological formulations due to its inhibitory effect on melanogenesis by affecting collagen synthesis and scavenger properties. However, ascorbic acid (AA) is quickly oxidized and decomposes in aqueous solution and to solve this problem, vitamin C derivatives were synthesized. In the present investigation, histopathological, morphometric and stereological studies were carried out to investigate the possible alterations caused by formulations containing AA or magnesium ascorbyl phosphate (MAP) in the epidermis. Gel creams either with or without 2% AA or its derivative were selected for investigation. Guinea-pigs were shaved on the back, and four areas of 1.5 cm(2) each were used for the experiments. One untreated area was used for control and the others for the application of gel cream formulations either with or without AA or its derivatives. The formulations were applied daily for 2, 4 and 8 weeks and biopsies were then obtained from each area using a dermatological punch. The material collected was analysed by histopathological, morphometric and stereological techniques. We observed that, under the present experimental conditions, whole formulations acted on the epidermis causing a thickening of the epithelium, with cells of larger volume in the granulose and spinous layers.