The main objective of this study is to analyze the effect of the professional environment on sick leaves. It is important in order to identify the potential policies to implement to control health expenditures (e.g. through the improvement of working conditions). This professional context is approximated by the Business sector. The database used - Hygie (2005-2008) - allows taking into account individual heterogeneity thanks to the longitudinal dimension. Sick leave probability is estimated through an individual fixed effects logit model and the duration (number of sickness absence days) is estimated through a fixed effects Poisson model. The results show that Business sector differ in sick leave duration rather than in the occurrence. Indeed, taking into account differences in health status and wages reduces the variability in sick leave probability between sectors by half. On the other hand, the sector remains decisive in explaining sick leave durations. This residual variability may refer to unobserved differences in working conditions, in the generosity of sick pay benefits or in job insecurity. These results may call into question the financing of sick leaves, which contrary to accidents at work and professional diseases, only depends on social security contributions.