This prospective study on Fixed Drug Eruption (FDE) was carried out between January 2003 to December 2006 in Dermatology department of Mymensingh Medical College Hospital & private chambers. This study was carried out with an objective to see the specific site of involvement and other clinical parameters in FDE due to cotrimoxazole. In each case, a detailed history was taken and a thorough physical examination was done by at least one dermatologist. Patients with suspected FDE, who had consented, were included in the study. Oral re-challenge test was done in each case after written or verbal consent of the patient or legal guardian. For oral re-challenge, usually half of the usual therapeutic dose of the suspected drug (s) was given first and reactions were observed and if no reaction, then full therapeutic dose was given and then again reactions were observed. In case of no reaction to one drug, the next drug was tested after 2 to 7 days. Age & sex distribution, number of attacks of FDE, number of lesions, distribution of sites of involvement were determined in each case of FDE. All informations were recorded in pre-tested data sheet. Among 93 patients of suspected FDE, 61 patients were confirmed as FDE with identified causes, of which 36 cases were due to cotrimoxazole (59.02%). Age range of patients was from 5 years to 65 years with mean of 24.92 years. Male was predominantly affected (M:F=6.2:1). In 50% cases presenting attack was the 2nd attack. Rest 50% had 3 to more than 10 attacks. Number of lesions was: 2-5 lesions in 50%, solitary lesion in 16.67%, 6-10 lesions in 13.89% and more than 10 lesions in 19.44% cases. Sites of involvement in cases of FDE due to cotrimoxazole (n=36) were as follows: lips 58.33%, genitalia 33.33%, oral 13.89%, trunk 38.89%, limbs 55.56%, hands 16.67%, feet 19.44%, face 19.44% and conjunctiva 2.78%.