This analysis presents a method for estimating the population of men who have sex with men (MSM) at the county and metropolitan area level in Texas. Surveillance data consistently demonstrate that MSM experience a high burden of HIV and other sexually transmitted infections (STIs). Numerous studies have shown that MSM are also vulnerable to many other health concerns such as suicide, substance abuse, domestic violence and assault, homelessness, and mental illness. However, compilation of rates of HIV, STIs, and other health issues is dependent on estimation of population denominators. In the absence of systematic, consistent, and direct assessment of sexual orientation and gender identity in national surveys, it is difficult to estimate the size of at-risk populations. Previous estimates at the national and state level have been calculated using varied methodologies. However, to date, statewide estimates at the county level have only been produced for the state of Florida. County-level and metropolitan area estimates of MSM population were produced using three modified models developed by Lieb et al. These models used data on population and same-sex households from the US Census, along with estimates of sexual behavior from the National Survey on Family Growth. These models produce an estimate of 599,683 MSM in Texas (6.4 % of the adult male population). Metropolitan areas with the highest percentage of MSM population include Dallas and Austin (10.3 and 9.8 %, respectively). County-level estimates of MSM population range from 1.0 to 12.9 %. These local estimates are critical to targeting vulnerable populations and effective allocation of resources for prevention and treatment programs.