Background: Absenteism can generate important economic costs. Aim: To analyze the determinants of the time off work for sick leaves granted to workers of a regional health service. Material and Methods: Information about 2033 individuals, working at a health service, that were granted at least one sick leave during 2012, was analyzed. Personal identification was censored. Special emphasis was given to the type of health insurance system of the workers (public or private). Results: Workers ascribed to the Chilean public health insurance system (FONASA) had 11 days more off work than their counterparts ascribed to private health insurance systems. A higher amount of time off work was observed among older subjects and women. Conclusions: Age, gender and the type of health insurance system influence the number of day off work due to sick leaves.Comment: in Spanish