Purpose Various disparities exist in HIV transmission among men who have sex with men (MSM). Pre-exposure prophylaxis (PrEP) has been shown to decrease the acquisition of HIV, but there is variation in uptake within the MSM population. We aim to characterise PrEP use and correlates of self-reported PrEP use in a large national sample of urban MSM in the USA.

Methods Using data from a geosocial-networking application, a national sample (n=3744) from the largest 50 metropolitan centres in the USA was obtained.

Results We found 18.1% (95% CI 16.8 to 19.3) of profiles reported using PrEP, with decreased reported PrEP use in younger MSM aged 18–24 years (adjusted OR (aOR)=0.5, 95% CI 0.3 to 0.7), obese MSM (aOR=0.5, 95% CI 0.3 to 0.9), black MSM (aOR=0.6, 95% CI 0.4 to 0.9) and MSM in the South (aOR=0.7, 95% CI 0.5 to 0.9).

Conclusion Significant disparities exist in PrEP reporting by age and among black, Southern US and obese MSM. More research is needed to better understand these disparities.