To study the role of pretransplant IgG anti-F(ab)2 gamma and IgG anti-Fc antibodies on the outcome of live related donor (LRD) kidney transplantation, serum samples from 60 recipients and 20 normal controls (NC) were tested using enzyme immunoassay. Patients with well-functioning grafts (WFG) after 1 year of follow-up had significantly higher IgG anti-F(ab)2 gamma activity expressed as mean optical density measured at 405 nm, i.e. 0.426 +/- 0.06 as compared to NC (0.167 +/- 0.046) or patients undergoing reversible rejection (RR) (0.145 +/- 0.043) and irreversible rejections (IR) (0.26 +/- 0.01). However, patients with IR had higher IgG anti-Fc activity (0.424 +/- 0.2) than the WFG group (0.1 +/- 0.02) and NC (0.095 +/- 0.02), with the RR group values in between (0.248 +/- 0.06). The same trend was observed when the data were analysed according to the serum creatinine levels. We conclude that in the LRD renal transplant situation, pretransplant serum IgG anti-F(ab)2 gamma activity has a protective effect on graft survival while IgG anti-Fc has a detrimental effect on graft outcome.