Pityriasis versicolor is one of the commonest skin conditions among tropical and sub¬tropical countries. The aim of the present work was to study the ultrastructural changes in hypopigmented lesions of pityriasis versicolor in order to understand the patho¬genesis of the disease. The study was done on 18 patients with extensive hypopigmented lesions of pityriasis versicolor. Skin punch biopsies were taken from hypopigmented lesions and from adjacent unaffected areas which served as a control. The results of the present study showed that the number of melanosomes in the melanocytes of hypo¬pigmented lesions and adjacent uninvolved areas were of insignificant difference. Also, there was insignificant difference between the number of melanoeomes in basal keratinocytes of hypopigmented lesions and adjacent uninvolved areas. On the basis of these results, the hypopigmentation in tinea versicolor may be due to decrease melaniz¬ation of melanosomes and abnormal distribution of melanosome granules throughout the keratinocytes.