CA-125, a commonly used tumor marker for epithelial ovarian cancer, is a glycoprotein found in normal tissues derived from coelomic epithelia. Increased serum levels of CA-125 have also been found in nongynecologic tumors and nonmalignant diseases involving the peritoneum. A few recent studies and sporadic case reports have reported increased CA-125 levels in patients with non-Hodgkin's lymphoma (NHL). In our study, we aimed to evaluate the serum levels of CA-125 in patients with NHL and determine its potential role to show disease activity in NHL. Serum levels of CA-125 were measured in 61 patients with NHL and were found to be correlated with clinical stage, site of involvement, and disease activity.