In order to investigate a possible immune regulation imbalance in familial Mediterranean fever (FMF), the T-cell subsets and interleukin (IL)-1 and -2 production were examined in 39 patients (32 consecutive; 7 previous) and 14 controls. Results in the FMF group indicated no change in total T-cells and B-cells. The number of supp T-cells and helper cells were significantly decreased, as compared to the controls (14 +/- 5.2, 19 +/- 4.6 vs. 31 +/- 4.6, 41 +/- 5.3, respectively), and the NK cells were significantly increased (16 +/- 4.8, 36 +/- 2.1). Peripheral blood monocytes from the patients with FMF produced higher amounts of IL-1 and lower amounts of IL-2 than those from the control subjects. The latter results were enhanced when the FMF group was subdivided on the basis of pretreatment with colchicine and presence of amyloidosis. This study, although preliminary, indicates an immune regulation imbalance in FMF patients. Further research is necessary to understand the interrelation of amyloidosis and colchicine treatment.