Background Sexually transmitted infections (STIs), and HIV especially, are a major health problem in Malaysia. The emergence of HIV infection has increased the importance of early and effective treatment of STIs as any delay may lead to enhance transmission or acquisition of HIV infection. A proper understanding of the patterns of STIs is necessary for effective planning and control strategies. The present study is designed to determine the changing pattern of STIs in the Genito-urinary Medicine Clinic (GUM), Hospital Kuala Lumpur (HKL). Objective To study the sociodemographic characteristics of patients with STIs attending the GUM Clinic in HKL and to analyze any changes in the pattern of STIs seen between the 2 study periods of 1995-1999 and 2001-2005. Method A retrospective review of case notes of new patients with STIs attending the GUM clinic, HKL was done during two study periods of 1995-1999 (Poster presentation on “Pattern of STDs” at 14th RCD, Asia-Australasia, 26-30 July 2000, KL, Malaysia by HB Gangaram et al) and 2001-2005. Results In 1995-1999, a total of 3150 STI patients were studied. Among them, 2016 (64%) were males and 1134 (36%) were females. In 2001-2005, a total of 2909 STI patients were examined, of which 1862 (64%) were males and 1047 (36%) were female. There was a decrease of 8.3% in the total number of cases seen in 2001-2005 as compared to 1995-1999. The decline was more evident with bacterial STIs which included syphilis, gonorrhoea, NGU and chancroid. Viral STIs which consisted of herpes genitalis, genital warts and HIV showed an increasing trend. A younger age group (20-39 years old) appeared to be infected with STIs in 2001-2005. Males outnumbered females in the ratio of 1.8:1, which remained unchanged in both the study periods. Based on ethnicity, there was an increase in the percentage of Malays being infected in STIs in the later study period. Syphilis was the commonest STI seen in both the study periods. The second commonest STI seen in 1995-1999 was gonorrhoea and non-gonococcal urethritis (NGU). In 2005, there were 184 patients with syphilis; 64% were heterosexuals; 39.6% homosexuals and 1.6% bisexuals. Majority (82%) were asymptomatic (latent syphilis with positive syphilis serology at presentation. Symptomatic patients with early infectious syphilis constituted 15% (Primary 8%; Secondary 7%). Screening for HIV was positive in 31 (16.8%) patients. HIV infection was noted to be the commonest STI associated with syphilis. Conclusion was an overall decline in the number of patients with STIs attending the GUM clinic, HKL. The decline was more evident with bacterial STIs; viral STIs however showed an increasing trend. Syphilis was still the commonest STI seen in the two study periods although the percentage has declined. Non specific urethritis has superseded gonorrhoea as the second commonest STI. HIV was found to be the commonest STI seen in association with syphilis.