All in-and out-patients, who came for drug eruption consultation at the Dermatology Clinic, Ramathibodi Hospital from December 1997 to November 1998 were included in this study. Medical histories and physical examinations were performed by one of the authors. In suspected cases, a skin biopsy was performed to confirm the diagnosis. Patch test and oral challenge test were performed in some patients who had maculopapular, fixed drug eruption and acute generalized exanthematous pustulosis, with informed consent. Among 80 patients, the most common cutaneous reaction was maculopapular rash. Antimicrobial, drugs were the most common causative agents. The patch test was positive in only one patient from 12 cases. The oral provocative test was positive in two patients from 4 cases. It is concluded that oral provocative test is still necessary to get a definite diagnosis of causative agent. The value of patch test needs further study.