Influence of surgical trauma on experimental metastasis in healing wounds is investigated using a transplantable murine mammary carcinoma cell line, TA3Ha. Intravenous injection of 10(5), 10(6), and 2 x 10(6) TA3Ha cells into syngeneic Strain A mice led to liver or kidney tumor development in none of the 96, ten, and ten mice tested, respectively. In contrast, injection of 10(5) cells into mice immediately after hepatic wedge resection performed using milliwatt carbon dioxide laser and electrocautery resulted in tumor formation at the site of trauma in 21/37 (57%) and 25/52 (48%) mice, (P less than 0.001) respectively. Similar results were obtained in mice subjected to partial nephrectomy using the laser (nine of 18) and electrocautery (eight of 13). These results clearly demonstrate that surgical trauma renders a nonprivileged organ susceptible to experimental metastasis formation, and that at least in this model both laser and electrocautery have similar effects. Tumor cell injection 1, 7, and 10 days posthepatic surgery resulted in 36%, 20%, and 0% tumor formation, respectively, indicating that the earlier events in wound healing support tumor implantation and/or growth better than those later on. Frequency of tumor formation at sites of trauma in the peritoneum induced by scalpel blade, laser, and electrocautery were 28%, 50% and 82%, respectively. Peritoneal tumors were seen in 33% of the nonsurgical mice. Skin incisions induced with the three above probes had little influence on experimental metastasis formation. Thus the influence of trauma on tumor formation is not uniform in every organ.