OBJECTIVE: To estimate the extent of early retirement and to examine risk factors for voluntary early retirement and disability pension in a cohort of nurses' aides. DESIGN: Register study including baseline questionnaire and register data covering all transfer incomes from 1991 to 2008 in a cohort of nurses' aides established in 1993 with a follow-up period of 15 years. SETTING: Nurses' aides working in nursery homes, homecare or hospitals. PARTICIPANTS: 3332 gainfully employed nurses' aides at the time of inclusion in the study. OUTCOME: Disability pension or early voluntary retirement. RESULTS: 16.2% of the population was granted disability pension and 27.1% entered early voluntary retirement in the follow-up period representing 11 186 lost working years with a direct cost in transfer payment amounting about euro410 million. Health-related risk factors for disability pension was long-lasting low-back pain (HR 2.27(95% CI 1.55 to 3.34), sick leave because of upper-extremity disorders (HR 2.18 (95% CI 1.08 to 2.11), and inflammatory rheumatic disease (HR 2.42 (95% CI 1.67 to 3.52)). Of non-health-related factors, low education, workers compensation case, evening work and high-rated perceived exertion at work all were minor risk factors for disability pension. The primary risk factor for early voluntary retirement was low education (HR 3.19 (95% CI 2.65 to 3.85)). CONCLUSIONS: 43.3% of nurses' aides gainfully employed in 1993 retired before due time during the follow-up period. Work-related factors at baseline only seemed to have a minor prognostic role. Risk factors for disability pension were mainly health-related factors, whereas economical factors seemed to influence the decision to choose early voluntary retirement. The number of persons and the amount of lost working years underscores the need of a more active counselling towards maintaining employment especially among those with persistent musculoskeletal disorders.