The objective of this study was to investigate aspartate-amino-transferase (AST), gamma-glutamyl-transferase (GGT), alkaline phosphatase (ALP), lactate-dehydrogenase (LDH) and acid phosphatase (AcP) activities and semen parameters (volume, pH, concentration, total sperm number (TSN), progressive motility, dead sperm, total morphological defect (TMD) and hypo-osmotic swelling test (HOST)) in seminal plasma of Arabian horses. Furthermore, correlations between enzyme activities and semen parameters were examined. The study was performed using seven healthy Arabian stallions of proven fertility, between I I and 17 years of age, from the Karacabey Stud Farm in Bursa, Turkey. Overall, 21 semen samples were collected from stallions during the breeding season from March to May. A significant negative correlation was observed between semen volume and concentration of TMD, AST, ALP (P<0.05) and LDH (P<0.01). pH showed a significant correlation with live:dead ratio, GGT activity (P<0.05) and progressive motility (P<0.01). All semen concentrations correlated significantly with TSN, TMD, ALP, AcP (P<0.01). Furthermore, significant correlations were found between live:dead ratio and TSN, HOST (P<0.05); TSN and ALP, AcP (P<0.01); progressive motility and HOST (P<0.01), GGT (P<0.001); AST and ALP, LDH, AcP (P<0.001); GGT and LDH (P<0.05); ALP and LDH, AcP (P<0.01) and LDH and AcP (P<0.001). No significant correlation was found between enzyme activities in stallion seminal plasma and semen parameters in different months, except for pH and HOST.