Corrosion in metal implants (stainless steel 316L) was followed up in 25 rats for periods of 1.5 to 14.0 months after insertion into the femur, back musles, or as an external fixation of the tibia using light and scanning electron microscopy. In the implants buried in back muscles and as an external fixation, mainly 'face' and pitting corrosion were detected in 90% of the implants, while in the intramedullary implants crevice, pitting and various 'holes' of irregular shape were evident in all implants. Calcium and phosphate deposits were also found on the intrafemoral implants. The corrosion in the implants was detected as early as 1.5 months but was quite variable. However, a progressive increase in the corrosion occurred concomitant with the length of time after implantation. The question is whether stainless steel metal implants presently in clinical use can be considered innocuous.