GST-$\pi$ is a tumour marker for a number of different cancers. it is a member of GST enzyme group that are associated with cellular detoxification by catalyzing the conjugation of reduced glutathione to hydrophobic electrophilic compounds and may influence mutagenesis and carcinogenesis. The aim of this study is to describe the distribution of GST-$\pi$ in childhood diffuse non-Hodgkin's lymphomas and to evaluate its role in the response ofpatients to chemotherapy. in this study GST-$\pi$ in 34 childhood diffuse non-Hodgkin's lymphomas with different histological types and localization was evaluated. (Mean age 7.35years, 19 male, 15 female with 5-52 months follow-up). Nine cases had lost their lives vvithout any response to chemotherapy. A negative relationship between response to therapy and GST-$\pi$ positivity is found. We condude that GST-$\pi$ may be an important marker for determining drug resistance in childhood diffuse malignant lymphomas. Long time follow-up and more studies are required to understand multi-drug resistance and prognostic role of drug resistance proteins in diffuse malignant lymphomas.