A study was conducted in Lima to determine the HTLV-1 infection rate among patients with different clinical patterns of Strongyloidiasis. This study included 21 patients with Strongyloides Stercoralis (St St) hyperinfection (Group 1), and a group which consisted of sex and age matched asymptomatic healthy individuals whose stools were negative (Control Group Group 2). A third group included 33 patients with "probable hyperinfection", and another group of 63 patients with intestinal Strongyloidiasis, without evidence of systemic disease, was included. Serum from each studied individual was analized to find HTLV-1/II and ELISA; positive cases were confirmed by Western Blot. The hyperinfection rate was significantly higher [85.7% (18/21)] compared to the control group [4.7% (1/21)] p<0.001. Likewise, the "probable hyperinfection" group was considerably higher [69.7% (23/33)] in comparison to the control group p<0.01. The group with intestinal Strongyloidiasis was [10% (6/62)] lower than patients with Strongyloides hyperinfection, but did not differ significantly (p>0.05) from the control group. In this last group 3/6 were HTLV-1 positive, and their follow-up showed they developed hyperinfection forms. We conclude that severe forms of St St are considerably associated to HTLV-1 infection in adults and children over 5 years of age. No cases with HTLV-II were detected.