The clinicopathologic features of twenty cases of follicular lymphoma (FL) in pediatric patients are described. Fifteen boys and five girls were 2 to 20 yr (mean 10 yr) of age at diagnosis. In ten cases (50%) the lymphoma was localized in lymph nodes and in ten cases (50%) in extranodal sites. Fifteen patients had stage I, two stage II and three stage III disease at the time of presentation. The faucial tonsils were the primary site in seven cases, other head and neck sites in five, inguinal lymph nodes in four and possibly another, and the abdomen in two. Six cases (30%) were classified as follicular small cleaved cell type (FSCC), five (25%) as follicular mixed small cleaved and large cell (FMC), and nine (45%) as follicular large cell (FLC). The architectural pattern was purely follicular (F) in five cases (20%), predominantly follicular (F greater than D) in six (30%), follicular and diffuse (F = D) in six (30%) and predominantly diffuse (F less than D) in three (15%). In one case a progression from F greater than D LC to F less than D LC was documented. All patients attained complete remission (CR). One died of acute lymphoblastic leukemia 7 yr after the original diagnosis of FSCC non-Hodgkin's lymphoma (NHL), but the others are all alive and free of disease with a follow-up ranging from 6 mo to 16 yr (median 4 yr). In three patients therapy was initially deferred with no known adverse influence on outcome.(ABSTRACT TRUNCATED AT 250 WORDS)