Two hundred and nine cases of non-Hodgkin's lymphoma have been analyzed retrospectively for the occurrence of spontaneous regression (SR). Complete, partial or minor SR was found in 18 out of 140 cases with nodular lymphoma and in 2 out of 69 cases with diffuse lymphoma. Thus, SR occurs far more frequently in nodular lymphoma than in the diffuse type. Within the nodular lymphoma group, SR is associated with long survival. It occurred in previously treated and untreated patients and in nodal and extranodal disease; the duration varied from a few weeks to many years but lasted one year or more in 7 cases with complete or partial SR.