Maintenance of Trypanosoma cruzi infection in Triatoma infestans was evaluated. Seventy nine fourth instar nymphs were followed by 12 months, after being fed in infected mice. The bugs were examined every month, fecal smears were done to document T. cruzi infection then the bugs were fed in "clean" (uninfected) mice. Thirty nine per cent of the bugs remained infected until death twenty three per cent cleared infection and remained uninfected until death and nineteen per cent alternated positive and negative results. Our experience agrees with the published papers in medical literature. Longevity of T. cruzi in the host depends mostly in the feeding of the bug; well fed bugs maintain infection, and long fasting correlates with infection clearance.