Serum LDH-isoenzyme studies revealed that in carcinoma cervix, the principal activity was confined to LDH-2 and LDH-3 with a significant rise in LDH-2 fraction when compared with the control values (P less than 0.001). Radiotherapy caused significant lowering of LDH-2 and LDH-3 (P less than 0.001 in each case). There was no relation of LDH-isoenzyme distribution in different clinical stages and morphological distribution within the tumor. Further, LDH-2 and LDH-3 were found to be lowered significantly in good and moderate clinical radiation response (CRR) groups (P less than 0.001 in each case) but in poor CRR group no significant change in LDH-2 and LDH-3 was observed following radiotherapy. LDH-isoenzyme determination in carcinoma cervix is very helpful in assessing the treatment response following radiotherapy and thus may be an important prognostic parameter.