Factors associated with hip osteoarthritis were studied in 2,490 subjects aged 55–74 years using data from the First National Health and Nutrition Examination Survey (NHANES-1). Pelvic radiographs were read for hip osteoarthritis using Kellgren-Lawrence scales; cases were defined by grade ≥2 changes. Subjects with missing radiographs and other data and those with grade 1 radiographic changes (n = 132) were excluded from analyses. Crude and adjusted odds ratios and 95% confidence intervals (Cls) were estimated from logistic regression analyses. Overall, the crude prevalence of hip osteoarthritis was 3.1% (73 of 2,358); 42 cases were unilateral, and 31 cases were bilateral. Age was significantly associated with hip osteoarthritis (adjusted odds ratios = 1.30 (95% CI 0.60–2.81), 1.69 (95% CI 0.83–3.44), and 2.38 (95% CI 1.15–4.92) for ages 60–64, 65–69, and 70–74, respectively). Other sociodemographic factors, obesity, and fat distribution were not associated with hip osteoarthritis. Age and hip trauma were strongly associated with hip osteoarthritis among men; however, among women, no factors were significantly associated with hip osteoarthritis. Hip trauma was significantly associated with unilateral but not bilateral hip osteoarthritis, while obesity was associated with bilateral but not unilateral hip osteoarthritis. These data suggest that etiologic factors associated with hip osteoarthritis may differ for males and females and for unilateral and bilateral hip osteoarthritis.