Immobilization of North American porcupines (Erethizon dorsatum) with tiletamine hydrochloride (HCl) and zolazepam HCl (Telazol^®) was evaluated in central Massachusetts (USA) during 1991 and 1992. Doses between 9 and 11 mg/kg resulted in a mean (±SD) induction time of 3.2 ±1.3 min and a mean (±SD) immobilization time of 44.2 ± 19.5 min. Induction time did not differ by dose, sex, capture method, or porcupine weight. Immobilization time differed by dose and porcupine weight but not by sex or capture method. Tiletamine HCl and zolazepam HCl seems to be an effective combination of drugs for immobilizing porcupines as long as sufficient time is allowed for recovery.