Male osteoporosis is underappreciated. Little is known about men's knowledge of osteoporosis and how much men are at risk. This study surveyed men's knowledge of osteoporosis and their risk factors with reference to women in the primary care setting in Macau, China. A convenience sample of 302 men and 635 women aged 18 to 90 years completed questionnaires comprising the Osteoporosis Knowledge Assessment Tool and the One-Minute Osteoporosis Risk Test. Their risks of osteoporosis were assessed with the Osteoporosis Self-Assessment Screening Test. Men and women, who were aged 55 years or below, had similarly limited knowledge of osteoporosis. People aged above 55 years had significantly less knowledge; men had less knowledge than women only in this age-group. If questions specific to women or menopause were excluded, men had similar knowledge as women. A higher proportion of men than women had risk factors as more men consumed alcohol or smoked tobacco. Similar proportions of men and women reported a loss of 1 inch in body height after age 40. After age 55, 29.2% men were at medium to high risk of osteoporosis. This study concludes that health education and primary prevention of osteoporosis should be promoted to men starting in middle-age.