As well as constituting a health problem, absence from work is also a socioeconomic problem, as it involves a number of health and financial benefits financed by the Social Security system. This investigation analyzes three theories that explain absence from work: a work/leisure approach; the “worker discipline” version of the wage efficiency theory; and the “work group rules”. These three theories attempt to explain voluntary absence, attributable to the worker’s own wish, rather than involuntary, which is the result of the impossibility of going to work. The analyses are carried out separately for the two companies of an urban transportation company and according to the type of issue (accident and illness).