In a group of 70 patients with multiple myeloma (MM), formed by 25 patients examined while establishing the diagnosis and 45 patients examined in different stages of the disease, the authors evaluated the relationship of the bromodeoxyuridine "labelling index" (BrdUrd-LI) of myeloma plasma cells assessed by the method of double immunofluorescence (using antibody BU-1) and selected laboratory indicators of the disease. In the whole group the median and mean values of BrdUrd-LI of myeloma plasma cells were 2.0 (0.6-4.4%) and 2.1 +/- 0.9%, in the group of 25 patients examined during diagnosis it was 1.8 (0.6-4.1%) and 1.9 +/- 0.9%, in the group of 45 patients examined during different stages of MM it was 2.4 (0.6-4.4%) and 2.4 +/- 0.8%. Neither in the whole group nor in the sub-groups any statistically significant correlations were found between BrdUrd-LI values and the degree of anaemia, values of S-creatinine, S-MIG, S-albumin, S-B2M, S-ferritin, S-thymidine kinase, S-IL-6, S-IL-2, S-kIL-2R, the percentage ratio of myeloma plasma cells in bone marrow and the synthetic index of myeloma plasma cells paraprotein.