The purpose of the present study was to compare serum calcium and magnesium concentrations in different ages in cows with or without retained placenta (RP) and to evaluate treatment of cows with RP with oxytocin versus oxytocin combined with Cal-Bor-Mag solution. Blood samples were obtained within 12 hours of parturition from different breeds of cows with and without RP (n=38 and 30 respectively). Serum Ca and Mg concentrations were analyzed by atomic absorption spectrophotometry. 38 cases of RP in different breeds of cows were treated by infusion of either Oxytocin dissolved in normal saline solution or oxytocin dissolved in Cal-Bor-Mag solutions. The intervals between parturition and initiation of treatment between 12-24 hours P.P. RP is the failure to expel all or part of the fetal membranes up to 12 hours after parturition. The positive response to the treatment was considered as the expulsion of the entire placenta within 2 hours after infusion. Ca levels in cows with retained placenta were significantly lower than those in the control group (without RP). Cows in the control group and those with retained placenta were divided into subgroups based on age (3-4, 5-7 years old). The serum Ca concentration of 3-4 years old cows with retained placenta was significantly higher (p<0.05) than those of 5-7 years old. Serum magnesium levels showed no difference. Six- ty percent of the cows treated with oxytocin in Cal-Bor-Mag solution responded positively to the treatment, compared to approximately thirty-nine percent of the cows treated with oxytocin in saline solution (p<0.05).