We compared the prognostic value of conventional cytogenetic analysis and established factors such as beta2-microglobulin and plasma cell labeling index in 70 patients undergoing autologous blood cell transplantation for multiple myeloma. Patients underwent transplantation 5 to 88 months (median, 20 months) after the initial diagnosis of myeloma. Factors studied were age, sex, beta2-microglobulin, response to prior therapy, plasma cell labeling index, cytogenetic analysis, bone marrow plasma cell percentage, lactate dehydrogenase and C-reactive protein. Twenty-eight of 65 patients (43%) had abnormal marrow cytogenetics. Overall survival measured from transplantation was significantly better in patients with normal cytogenetics than in those with abnormal cytogenetics (median survival, 25 vs 12 months, P = 0.003). Progression-free survival was better, with median times of 12 vs7 months, respectively (P = 0.005); overall survival measured from the time myeloma was first diagnosed was also longer, with median survivals of 62 and 39 months, respectively (P = 0.001). Median plasma cell labeling index was 1.5% in patients with abnormal cytogenetics and 0. 2% in those with normal cytogenetics (P < 0.001). Abnormal bone marrow cytogenetics predict poor survival after blood cell transplantation for myeloma. There is a significant correlation between abnormal cytogenetics and high plasma cell labeling index, suggesting that certain cytogenetic abnormalities may offer a proliferative advantage to myeloma cells.