The welfare assessment of horses includes the evaluation of their ability to cope with the challenges of theirenvironment and of work given to them. The aim of this study was to evaluate the welfare of 12 clinically healthyhorses from a riding school, using physiological indicators. Double determinations were made (in winter and inspring of 2011) by a set of two tests each time, before and after physical effort. The clinical parameters (heart andrespiratory rate) were in the normal range at 20 minutes after effort, decreasing towards the resting values. Slightlyhigher values were recorded in the spring comparing with the winter, but the differences were not statisticallysignificant (P>0.05). Even if were in the normal range, the results of the haematology tests and the blood sugarvalues showed clearly the response of the horses’ organisms to exercise. The serum cortisol concentrations presentedan effort dependent elevation and higher values of the basic level were observed in the spring than in winter. Theother stress-response indicator recorded, the neutrophyle-lymphocyte ratio, showed dynamics correlated with that ofthe cortisol level. The physiological indicators tested in this study proved their real value in the riding horses’welfare assessment.