Discordant lymphomas, in particular nodal large-cell lymphomas with marrow small-cell lymphoma, were discovered recently, and the prognosis of patients with such disease has been discussed. The small cells were reported to be small lymphocytic or small cleaved lymphoma cells. We have detected, by kappa-lambda imaging (KLI) with delta-curves, using a flow cytometer, small lymphoma cells in the peripheral blood (PB) and bone marrow (BM) of 41 untreated patients with various B-cell lymphomas expressing surface Ig (sIg+BCL), and evaluated their clinical and prognostic significance. Small cells were found in approximately 90% (37 of 41) of sIg+BCL patients when either PB or BM was analyzed and, overall, the presence of small cells correlated well with the disease activity. However, in some patients, a few cells remained in the PB (16%) or BM (27%) even when they were in remission, whereas in others, the cells were presented in the PB or BM several months before relapse. These results suggest that the detection of small cells in PB or BM by KLI may be helpful for screening and monitoring patients with sIg+BCL. When the patients were subdivided into three groups (normal, low, and high amplitude), according to the abnormal grade criteria of the delta- curves, which were based on the results of both PB-KLI and BM-KLI, the survival of the high-amplitude group tended to be shorter than that of the normal group (P = .068), which was particularly marked when the follow-up period exceeded 2 years. Moreover, as the group grading worsened (normal less than low less than high), the complete response rates deteriorated (100%, 71%, and 60%, respectively) and the respective relapse rates after complete remission increased (17%, 40%, and 67%). Thus, the determination of the proportion of small lymphoma cells in PB and BM by KLI may be useful for predicting the prognoses of patients with sIg+BCL.