The authors retrospectively reviewed medical records of patients who were diagnosed as having drug-induced urticaria at Siriraj Hospital of Mahidol University (Bangkok, Thailand) between October 2004 and April 2007. One hundred and forty-seven drugs were presumed as causing acute urticaria. Females were affected more commonly than males. The most frequent drug groups were antibiotics, followed by non-steroidal anti-inflammatory drugs (NSAIDs). The most common culprit drugs were ceftriaxone, cephalexin, amoxicillin and diclofenac, respectively. The median duration of onset and of clinical remission were 18 hours and 24 hours, respectively. Antibiotics were the most frequent causes of drug-induced urticaria, of which cephalosporins were the most common causative drugs. Oral NSAIDs significantly had the shortest median onset of urticaria. After discontinuing the culprit drugs, the reactions usually disappeared within a few days.