There is controversy about the protective effect of condoms in preventing sexually transmitted diseases (STDs). This paper summarizes recent studies that assess the association between condom use and the prevalence of various STDs. Because condom use is considered a marker for sexual partnerships with greater risk of STD transmission, limited evidence of protection has been found among those reporting condom use compared to non-users. Previously, methodological issues have impacted the performance of valid studies on condom effectiveness including inability to determine consistency and correctness of use or the infection status of partners. These assessments are critical to interpreting data from condom studies since they tend to confound effectiveness and underestimate the protective effect of condom use. Recent studies have assessed these issues and found that consistent condom use is associated with lower rates of gonorrhea, chlamydia, syphilis, trichomonas (women) and genital herpes than inconsistent use. Pelvic inflammatory disease may be decreased and HPV-associated lesions may regress faster. While consistent use has been found to reduce STD, incorrect use undermines this benefit, especially for heterosexual men. Thus, while non-use is a significant factor affecting condom use failure, consistent and correct use of condoms is an important strategy in reducing STD risk.