Thirty-one patients were diagnosed by morphologic and immunophenotypic features as having primary Ki-1 anaplastic large-cell lymphoma (Ki-1 ALCL). the median age was 35 years (range, 4 months to 78 years); the male:female ratio was 18:13. B symptoms were observed in 13 patients. Peripheral adenopathy was present in 26 patients, while mediastinal adenopathy occurred in five. There was extranodal disease in 13 patients; the most common extranodal site was skin with seven affected. Seventeen patients had stage III/IV disease. Immunophenotypes were T cell in 24 patients and B cell in four patients; immunophenotype could not be determined in three patients. Cytogenetic abnormalities in chromosomes 2, 5, and 7 were detected in three patients. Although therapy was heterogeneous, the actuarial 2-year survival was 73%. Two-year disease-free survival was 39% for all patients; for stages I and II, it was 62% compared with 20% for stages III and IV (P = .001). Complete remission (CR) occurred in 21 of 23 patients receiving combination chemotherapy; however, nine relapses, including six of seven stage IV patients, occurred within 21 months of diagnosis. Preliminary observations suggest that Ki-1 ALCL may have a quiescent phase in the rare patient with only localized skin disease. However, the disease generally behaves as an intermediate- to high-grade lymphoma, and patients with Ki-1 ALCL should receive curative-intent combination chemotherapy.