Wang, LinweiMoqueet, NasheedLambert, GillesGrace, DanielRodrigues, RickyCox, JosephLachowsky, Nathan J.Noor, Syed W.Armstrong, Heather L.Tan, Darrell H. S.Burchell, Ann N.Ma, HuitingApelian, HerakKnight, JesseMessier-Peet, MarcJollimore, JodyBaral, StefanHart, Trevor A.Moore, David M.Mishra, Sharmistha2022-03-162022-03-1620192019Wang, L., Moqueet, N., Lambert, G., Grace, D., Rodrigues, R., Cox, J., Lachowsky, N. J., Noor, S. W., Armstrong, H. L., Tan, D. H. S., Burchell, A. N., Ma, H., Apelian, H., Knight, J., Messier-Peet, M., Jollimore, J., Baral, S., Hart, T. A., Moore, D. M., & Mishra, S. (2019). “Population-Level Sexual Mixing According to HIV Status and Preexposure Prophylaxis Use Among Men Who Have Sex With Men in Montreal, Canada: Implications for HIV Prevention.” American Journal of Epidemiology, 189(1), 44-54. DOI: https://doi.org/10.1093/aje/kwz231https://doi.org/10.1093/aje/kwz231http://hdl.handle.net/1828/13800The authors thank the Engage-Montreal office staff and community engagement committee members, as well as their community partner agencies.Using cross-sectional survey data (Engage, 2017–2018) from 1,137 men who have sex with men, ≥16 years old, in Montreal, we compared observed human immunodeficiency virus (HIV) seroconcordance in previous- 6-months’ sexual partnerships with what would have been observed by chance if zero individuals serosorted. Of 5 recent partnerships where both individuals were HIV-negative, we compared observed concordance in preexposure prophylaxis (PrEP) use with the counterfactual if zero individuals selected partners based on PrEP use. We estimated the concordance by chance using a balancing-partnerships approach assuming proportionate mixing. HIV-positive respondents had a higher proportion of HIV-positive partners (66.4%, 95% confidence interval (CI): 64.0, 68.6) than by chance (23.9%, 95% CI: 23.1, 24.7). HIV-negative respondents (both on and not on PrEP) had higher proportions of HIV-negative partners (82.9% (95% CI: 81.1, 84.7) and 90.7% (95% CI: 89.6, 91.7), respectively) compared with by chance (76.1%, 95% CI: 75.3, 76.9); however, those on PrEP had a higher proportion of HIV-positive partners than those not on PrEP (17.1% (95% CI: 15.3, 18.9) vs. 9.3% (95% CI: 8.3, 10.4). Those on PrEP also had a higher proportion of partners on PrEP among their HIV-negative partners (50.6%, 95% CI: 42.5, 58.8) than by chance (28.5%, 95% CI: 27.5, 29.4).The relationship between PrEP and sexual-mixing patterns demonstrated by less population-level serosorting among those on PrEP and PrEP-matching warrants consideration during PrEP roll-out.enHIVMSMPrEPPrEP-matchingserosortingsexual mixing patternsArticleSchool of Public Health and Social Policy