In Sweden, a change of the legislation for sickness absence became effective on 1st October, 1995. The purpose of the change was to reduce costs for sickness absence by exclusion of non-medical criteria for sick-listing, more part-time sick-listing and faster rehabilitation. This study was conducted in order to describe and analyse certification practice of various physician categories, before and after the change in legislation. Thirty-one thousand seven hundred and thirty certificates for sickness absence, collected by the local offices of the National Social Insurance Board in eight Swedish counties, fulfilled the inclusion criteria. The number of certificates decreased temporarily. The number of certified net days, i.e. crude days multiplied by degree, tended to increase and there was no shift from full to partial sick-listing during the period. There were small changes regarding case mix, i.e. patient characteristics, and sick-listing physician category. The results were almost unchanged when these small changes were taken into account. General practitioners issued significantly shorter periods of sick-leave than the other categories both years. The goals of the legislative change were thus not met. The result of the study indicates that other factors than the legislation may be more important for physicians' practice.