Epicondylitis is a common disorder of the arm, yet the role of individual- and work-related factors has not been addressed in a population study. The aims of this study were to estimate the prevalence of lateral and medial epicondylitis and to investigate their risk factors. The target population of this study comprised a representative sample of people aged 30-64 years residing in Finland during 2000-2001. Of the 5,871 subjects, 4,783 (81.5%) were included in this study. The prevalence of definite lateral epicondylitis was 1.3%, and that of medial epicondylitis was 0.4%. The prevalence did not differ between men and women and was highest in subjects aged 45-54 years. Current smoking (adjusted odds ratio (OR) = 3.4, 95% confidence interval (CI): 1.4, 8.3) and former smoking (OR = 3.0, 95% CI: 1.3, 6.6) were associated with definite lateral epicondylitis. An interaction (p = 0.002) was found between repetitive movements of the arms and forceful activities for the risk of possible or definite lateral epicondylitis (for both repetitive and forceful activities vs. no such activity: OR = 5.6, 95% CI: 1.9, 16.5). Smoking, obesity, repetitive movements, and forceful activities independently of each other showed significant associations with medial epicondylitis. Epicondylitis is relatively common among working-age individuals in the general population. Physical load factors, smoking, and obesity are strong determinants of epicondylitis.