An epidemiological survey conducted in Senegal in 2004 among men having sex with men (MSM) revealed high HIV prevalence and a high rate of risky behaviors within this population. Consequently, several prevention campaigns targeting MSM were implemented. A second survey was carried out in 2007 to assess the impact of these measures. This paper aims to examine trends in HIV and STI prevalence and in sexual behaviors between 2004 and 2007. The two surveys were conducted in four urban sites among 440 and 501 MSM--recruited using the snowball sampling method--in 2004 and 2007, respectively. A similar methodology was applied for both surveys. This consisted of a closed-ended questionnaire concerning socio-demographic, behavioral, and biomedical information plus a clinical examination including urine and blood tests to detect STIs and HIV infection. Between 2004 and 2007, the frequency of different sexual practices reported by MSM remained stable, but condom use for each type of sexual practice rose. The percentage of men who reported consistent condom use during previous-month anal sex has increased by about 35% (p<0.01). The percentage of men who reported consistent condom use during previous-month non-commercial sex with women has increased by 14% (p<0.01). HIV prevalence remained stable from 22.4% [95% CI: 18.6-26.8] in 2004 to 21.8% [95% CI: 18.3-25.7] in 2007 (adjusted OR = 1.05, p=0.8). Gonorrhea prevalence decreased from 5.5% [95% CI: 3.6-8.3] in 2004 to 2.6% [95% CI: 1.5-4.5] in 2007 (adjusted OR=0.5, p=0.07). The prevention campaigns, STI and HIV care and support programs conducted in Senegal among MSM have been followed by a reduction of risk-taking behaviors and STI prevalence among this population. Specific targeting of this group within HIV/STI prevention programs seems to be effective in decreasing sexual infections.