OBJECTIVES: 1.  Assess the proportion of anogenital warts to the total number of Sexual Transmitted Infection (STI) and 2.  Quantify the direct medical costs of anogenital warts from patient perspective METHODS: A prospective observational study was conducted in STI Clinic at Bangrak Hospital, Bangkok, Thailand from June 2008-September 2009. The proportion of anogenital warts to the total number of STI was calculated from the database of Bangrak Hospital. A total of 131 patients with clinically diagnosed anogenital warts were recruited. After baseline assessment, the patients had three additional follow-up-visits at day 7, month 1, and month 3. On each visit, patients were examined and interviewed for healthcare costs, work productivity loss and activities impairment. At month 6, telephone assessment for the signs of disease recurrence was done. Patients were treated according to standard medical practice. RESULTS: The proportion of anogenital warts to the total number of STI in 2008 was 14.6 %.  The mean age (SD) of the study subjects was 28.2 years (7.4 years). Males and females were approximately equal (males 51.9%, female 48.1%).  Most of them were employed (51.1%), the rest were sex workers (25.2%), and students (18.3%). The majority (83.2 %) were treated with podophyllin paints.  At 6 months, 55.0% were cured, 25.2% still had ongoing genital warts, 5.7% had a recurrence, 12.2 % were lost to follow up and 1.5 % was discontinued. The median direct medical costs were 998 (range 130-4060) Thai Baht. All patients were treated as out-patient cases and 71.7% came to hospital without work absenteeism. After having genital warts lesion, work productivity was reduced to 83.0% (17.3) and daily activity was also declined to 82.4% (14.4) from baseline.  CONCLUSIONS: Anogenital warts are common STI and tend to be recalcitrant to treatment. They also lead to the reduction on work productivity and daily activity.