Background: The differential diagnosis of ascites is a common clinical problem and the serum-ascites albumin gradient (SAAG) can be helpful in making a diagnosis. However, the serum-ascites albumin gradient does not differentiate malignancy from other causes of low gradient ascites. Aims and objectives: The aim of the study was to determine if ascitic fluid total lactate dehydrogenase concentration can be used to differentiate malignant from non malignant ascites. Materials and methods: This was a cross sectional study carried out over 11 months. It included one hundred patients with ascites seen at the University of Nigeria Teaching Hospital, Enugu and they were evaluated to determine the cause of ascites. The patients were divided into two groups after investigations were done to determine the aetiology of the ascites: A. Patients with malignant ascites (50 patients) B. Patients with non malignant ascites (50 patients) Serum and ascitic fluid total lactate dehydrogenase (LDH) concentration were checked in all patients using the pyruvate to lactate method. The principle of this method is that lactate dehydrogenase catalyzes the conversion of pyruvate to lactate. Data obtained were entered into statistical package for social sciences (SPSS) version 23.0 and analyzed. Mann Whitney U test was used to determine if there was any significant difference in the values of ascitic fluid total lactate dehydrogenase concentration between the two groups of patients. Receiver xvi Operating Characteristics (ROC) was used to test for the accuracy of ascitic fluid total lactate dehydrogenase concentration in classifying malignant and non malignant ascites.