The behavior of leiomyosarcoma (LMS) is site related, but there are limited data on such tumors presenting in the paratesticular region. Cases diagnosed as LMS of the paratesticular region from the files of three institutions were reviewed. Immunohistochemistry was performed in cases with available blocks, and follow-up information was obtained. From 31 cases originally diagnosed as LMS, 24 were retained after review. These were from men aged 34-86 years (mean 62 years; median 64 years) and involved the testicular tunica (10), spermatic cord (10), scrotal subcutis and dartos muscles (1 each), and the epididymis (1). Tumors ranged in size from 2-9 cm (mean 5 cm; median 4 cm). On immunohistochemical staining they expressed muscle-specific actin (13 of 14), smooth muscle actin (10 of 10), desmin (16 of 17), and CD34 (3 of 9); all of the latter three were strongly desmin-positive. Focal reactivity for cytokeratin (3 of 8) and S-100 protein (1 of 8) was seen. Follow-up information was available in 14 patients. Four (29%) had recurrences, in one case four times. Metastases to lymph nodes, lungs, or liver were seen in four patients (29%), of whom two had prior recurrences. Ten were alive with no evidence of disease (ANED), and four were dead of disease (DOD). Comparing outcome with tumor grade, all seven patients with grade 1 tumors (of whom two had recurrences) and all three with grade 2 tumors were ANED, whereas all four patients with grade 3 tumors were DOD. In summary, paratesticular LMSs are rare neoplasms. The majority in this site are low-grade, although high-grade lesions behave aggressively.