In this study. calcium (Ca), phosphorus (P) and alkaline phosphatase (AP) levels of the blood serum of cows with retained placenta (RP) were measured and the role of these parameters on the etiology of the RP was investigated. A total of 28 different ages and breeds of cows, of which 14 (group I) had retained placenta and 14 (group 2) discharged fetal membranes (within 3-8 hours of delivery) were used as the material of the study. Additionally, these two groups were divided into two subgroups, according to the sexes of their calves, and three subgroups called groups A (3 years). B (4-6 years) and C (greater than or equal to7 years), according to their ages. Their serum levels of Ca, P and AP levels were determined by spectrophotometry. The serum levels of Ca, P and AP were found to be respectively 7.93+/-0.38 mg/dl, 6.02+/-0.52 mg/dl and 14.29+/-0.97 IU/L in group 1 and 8.51+/-0.39 mg/dl. 6.18+/-0.50 mg/dl and 17.15+/-1.62 IU/L in group 2, with no difference between the groups (Pgreater than or equal to0.05).