OBJECTIVES: We examined the effects of chronic stress with modelling different shift work schedules in animal experimental model. METHODS: Internationally most frequently used night shift schedules were applied in three groups of animals (4DL/3LD; 8DL/6LD; 2DL/2LD) beside a group kept in normal LD cycle (12 hour light-L/12 hour dark-D=control group). Groups were divided in two parts, one of them were exposed to CMS. Degree of anxiety was evaluated in light-dark box. Differences between groups according to variables (sex, lighting regimens and CMS) and time spent in light, number of changing compartments and latency of changing dark to the light section were examined with multiple one-way analysis of variance. Plasma concentrations of corticosterone and testosterone were measured after 4 weeks of exposure to stress procedures, concentrations were determined by radioimmunoassay. RESULTS: In groups kept under different lighting schedules compared to control group, significant differences were found: animals kept in 4DL/3LD (p=0.05, p=0.079 /nearly significant/ p=0.011) and 2DL/2LD (p=0.025, p=0.001, p=0.045) schedules spent less time in light, latency increased, while no statistically significant differences were found in 8DL/6LD group in any of the variables (p=0.113, p=0.118, p=0.45). We found that groups kept in different lighting schedules and exposed to chronic stress kept their circadian rhythm (corticosterone: p=0,095 – border line statistical significance; testosterone: p=0.004), while groups kept in different lighting schedules but not exposed to chronic stress lost circadian rhythms (corticosterone: p=0.071 for 12-hour component; testosterone: p>0.20). CONCLUSIONS: According to light-dark box test and hormonal examinations it seems, that shifts different than normal light/dark regimen lead to anxiety also without CMS, and may have been harder load than the CMS procedure. Group 8DL/6LD shows the closest approximations of parameters observed in LD group suggesting that this schedule applied in shift work is less harmful to health, and provides the best way of regeneration.