Comparison of LyP and HD suggests that these are closely related lymphoproliferative disorders that may occur in the same patient, share similar histologic features, and have the same immunologic phenotype. Recent studies of the molecular biology of both disorders confirm a similar distribution of T-cell receptor gene rearrangement patterns. The study of LyP, although a rare and benign disorder, has improved our understanding of HD, which appears, in some cases, to be a proliferation of malignant activated T lymphocytes. Further analysis of LyP may lead to a better understanding of the spontaneous regression of this disorder and result in new methods for treatment of HD.