The effects of long-term drought stress on chlorophyll, proline, protein and hydrogen peroxide (H2O2) contents, malondialdehyde (MDA) in terms of lipid peroxidation and on the changes in the activities of antioxidant enzymes such as superoxide dismutase (SOD, EC 188.8.131.52), ascorbate peroxidase (APX, EC 184.108.40.206), catalase (CAT, EC 1.1 1.1.6) and peroxidase (POX; EC 220.127.116.11) in the leaves of pea (Pisum sativum L.) were studied in field conditions. Chlorophyll and protein contents in leaves decreased significantly with increased drought stress. The proline content increased markedly under water deficit. MDA amounts were elevated as a result of water shortage, whereas H2O2 content changed slightly in pea leaves exposed to drought stress. Drought stress markedly enhanced the activities of SOD, CAT and PDX but slightly changed the activity of APX. We conclude that in field conditions, long-term water shortage increased the susceptibility to drought in peas.