A 12-year-old white female with recurrent Burkitt's lymphoma had a spontaneous remission associated with a localized herpes zoster infection. The remission lasted nearly 2 months before the tumor recurred in the central nervous system. LDH isoenzyme determinations done on an earlier ovarian tumor and serum at time of bone marrow relapse showed different predominant LDH isoenzyme patterns. These data might be interpreted as showing that different malignant cell clones were responsible for ovarian and bone marrow relapses. Studies to elucidate the mechanism of spontaneous remission at the time of zoster infection demonstrated serum factor(s) which stimulated normal B lymphocytes.