BACKGROUND: To date, research on men who have sex with men (MSM) has largely focused on their sexual health needs and on men recruited from gay-orientated venues. National probability survey data provide a rare opportunity to examine the broader sociodemographic, behavioural, and health profiles of MSM, defined as men who reported ≥1 male sexual partner(s) in the past 5 years, and thus regardless of their sexual identity, in comparison to men reporting sex exclusively with women (MSEW) during this time, and also the extent that health inequalities cluster. METHODS: Britain's third National Survey of Sexual Attitudes and Lifestyles (Natsal-3), a probability sample survey, interviewed 15,162 people aged 16-74 years (6,293 men) during 2010-2012 using computer-assisted personal-interviewing with a computer-assisted self-interview. We used multivariable regression to compare MSM relative to MSEW in their reporting of variables, individually and collectively, corresponding to three domains: physical, mental, and sexual health. RESULTS: Among all men, 2.6 % (n = 190) were defined as MSM, of whom 52.5 % (95 % CI: 43.6 %-61.2 %) identified as gay. MSM were as likely as MSEW (n = 5,069) to perceive their health was 'bad'/'very bad', despite MSM being more likely to report a long-standing illness/disability/infirmity (adjusted odds ratio, AOR: 1.46, 95 % CI:1.02-2.09), treatment for depression/past year (2.75, 1.69-4.47), and substance use (e.g., recreational drug use/past year: 3.46, 2.22-5.40). MSM were more likely to report harmful sexual health behaviours, e.g., condomless sex with ≥2 partners/past year (3.52, 2.13-5.83), and poor sexual health outcomes, including STI diagnosis/es (5.67, 2.67-12.04), poorer sexual function (2.28, 1.57-3.33), both past year, and ever-experience of attempted non-volitional sex (6.51, 4.22-10.06). MSM were also more likely than MSEW to report poor health behaviours and outcomes both within and across the three health domains considered. Of all MSM, 8.4 % had experienced poor health outcomes in all three domains - physical, mental, and sexual health - in contrast to 1.5 % of all MSEW. CONCLUSIONS: MSM are disproportionately affected by a broad range of harmful health behaviours and poor health outcomes. Although often observed for a minority of MSM, many health inequalities were seen in combination such that policies and practices aimed at improving the health and well-being of MSM require a holistic approach, regardless of clinical specialty.