Thyroid function and morphology, liver morphology, some metabolic indices, haematological parameters and growth performance of fattening pigs fed 00-rapeseed meal (00-RPM) were examined. The control group was fed on a standard diet containing 6% sunflower seed meal (SM) during the growing period and 8% during the finishing period. The first experimental group was fed a diet in which SM was replaced by equal (6% and 8%) amounts of 00-RPM. The second experimental group was fed with a higher (8% and 10%) amount of 00-RPM. There were no significant differences between the control and experimental groups in the serum concentrations of triiodothyronine (T3) and thyroxine (T4). Thyroid gland and liver weights were significantly (P < 0.01) higher in both groups fed 00-RPM than in the group fed SM. The epithelium of the thyroid gland was cuboidal or columnar and the follicular area was moderately enlarged in pigs fed 00-RPM. Marked changes in liver histology were not observed. The 00-RPM diet increased (P < 0.01) the serum values of total proteins in the first fattening period. At the end of fattening both groups fed 00-RPM had higher (P < 0.05; P < 0.01) concentrations of plasma glucose than the control group. The inclusion of 10% of 00-RPM during the finishing period increased (P < 0.05) the serum values of insulin. Daily weight gain during the growing and the finishing period was higher (P < 0.05) in the experimental groups than in the control group. The results suggest that 6-10% 00-RPM can be used as a protein source in the diet of fattening pigs without poisonous side effects.