The aim of this prospective study was to detect a possible development of trapezius myalgia likely to be work-related in initially healthy female packers. Symptoms were recorded on a five-step intensity scale in a daily diary and in an interview at ten-week intervals. All of the subjects were interviewed concerning assumed risk factors during work and leisure time, and a clinical examination was performed. Within their first year of employment, 17 of 30 subjects developed work-related trapezius myalgia of sufficient intensity to be classified as patients. The median time before a clinically confirmed patient status was 23 (range 6-51) weeks. The symptoms showed a fluctuating pattern, decreasing on the weekends and during some holidays. In conclusion, likely work-related trapezius myalgia of a nonchronic character showed a high one-year cumulative incidence at a plant with repetitive light work.