The trapping function of the heterotopic splenic autotransplants (HSA) in 13 polytraumatized patients, aged 5-38 yr, was evaluated using heat damaged technetium-99m-labeled autologous red blood cells in early (1-7 mo) and late (3-4.5 yr) period after heterotopic autotransplantation to the omentum. The intensity of tracer accumulation was graded in comparison to the liver uptake. The splenic tissue surface was calculated on anterior projection each time. The shapes of the transplants were compared and new uptake foci suggesting spontaneous splenosis were looked for on both scans. The average surface of HSA was 28.2 (+/- 14.7) cm2 on early and 44.1 (+/- 14.3) cm2 on late examination (p less than 0.003) and the increase in intensity of tracer accumulation on both occasions was significant as well (p less than 0.0001). In three patients, some additional splenotic foci were found on follow-up scans. Howell-Jolly bodies in peripheral blood were detected in six of eight patients in early and remained detectable in lower number in three of eight patients on follow-up. No serious infection was noticed in our group of patients. Our work confirmed the excellent survival rates of HSA with improving trapping function and no important spread from original implantation site on long-term follow-up.