This prospective multi-centre study was carried out in the Department of obstetrics and gynaecology of Bangabandhu Sheikh Mujib Medical University, Dhaka Medical College Hospital and Bangladesh Medical College Hospital, Shaheed Suhrawardy Medical College Hospital, Dhaka, Bangladesh, during the period of January 2008 to December 2009, to establish the raised level of serum LDH and serum CA-125 in pre-operative discrimination of benign and malignant ovarian cancer to be used as a diagnostic marker and its validity by determining sensitivity, specificity, accuracy, positive predictive value (PPV) and negative predictive value (NPP). A total number of 141 consecutive suspected subjects of ovarian tumour admitted in the above mentioned hospitals and enrolled for surgical management were included in this study. Serum LDH was done in all these subjects and they were followed up from the admission upto the postoperative tissue diagnosis of live tumor in respective pathology departments for histopathological correlation. The patients who were diagnosed as malignant placed in Group I and diagnosed benign ovarian tumor placed in Group II. Serous cystadenoma and mucinous cyst adenoma were more common in benign tumors, which were 38.9% and 20.4% respectively. However, more than a half (57.1%) had serous cyst adenocarcinoma in malignant tumors. In LDH for evaluation of malignancy, true positive 16 and false positive 18, false negative 12 and true negative 95 cases. LDH and serum CA-125 level (combined, i.e. both positive) for evaluation of malignancy, true positive 14 and false positive 0, false negative 14 and true negative 113 cases. LDH/serum CA-125 level (anyone positive) for evaluation of malignancy, true positive 25 and false positive 37, false negative 3 and true negative 76 cases. The validity of LDH were sensitivity 57.1%, specificity 84.1%, accuracy 78.7%, positive predictive values 47.1% and negative predictive values 88.8% for malignancy of ovarian tumour. The validity of CA-125 were sensitivity 78.6%, specificity 82.3%, accuracy 81.6%, positive predictive values 52.4% and negative predictive values 93.9% for malignancy of ovarian tumour. The validity of LDH and serum CA-125 level (combined, i.e. both positive) for malignant ovarian tumour it was found that sensitivity 50.0%, specificity 100.0%, accuracy 90.1%, positive predictive values 100.0% and negative predictive values 89.0%.