Background : Ribonuclease (RNase) are widely distributed in various organs and body fluids, including serum, urine, saliva, and cerebrospinal fluid. Small amounts of extracellular (( exocrine)) forms of this enzyme are secreted by the normal human pancreases into the gut, have observed increased levels of serum RNase in a series of patients with cancer of ovary. They have suggested that this might represent increased enzyme synthesis by proliferating tumor cell within the ovary. Objective : The aim of this study was to evaluate acid and alkaline RNase activities in serum of women presented with benign and malignant ovarian tumors with respect to these of healthy women. Method : A total of twenty nine women patients (15 women with benign ovarian tumor and 14 women with malignant ovarian tumors) were included.. Their age were 28-60 years the two groups were compared with a group of age matched (16 healthy women). Five milliliter of blood samples were obtained from patients by vein puncture just before surgery, as well as the from healthy women. Protein concentration was determined for patients and healthy individuals, and RNase activity for both the acid and alkaline forms were estimated by spectrophotometric methods with yeast RNase as the substrate. Results : Results revealed that patients group with ovarian malignancy had significant increase(p<0001) in both serum alkaline and acid RNase activity when compared with patients of benign tumors and the control group. There were significant (p<0.05).increases in serum alkaline and acid RNase specific activities, in women with ovarian cancer when compared with women of benign tumors and the control group. Conclusion : Estimation of alkaline and acid RNase activity is a promising approach for the detecting of ovarian cancer.