Nine-banded (n = 47) and great (n = 31) long-nosed armadillos (Dasypus novemcinctus and Dasypus kappleri) were immobilized for clinical examination and collection of biological samples as part of a wildlife rescue during the filling of a hydroelectric dam (Petit Saut, French Guiana) from May 1994 to April 1995. Three intramuscular (i.m.) anesthetic combinations were evaluated: (1) tiletamine/zolazepam (T/Z) at a dose of 8.5 mg/kg in 12 nine-banded long-nosed armadillos (NBA) and 10 great long-nosed armadillos (GLA), (2) ketamine at 40 mg/kg combined with xylazine at 1.0 mg/kg (K/X) in 18 NBA and nine GLA, and (3) ketamine at 7.5 mg/kg combined with medetomidine at 75 μg/kg (K/M) in 17 NBA and 12 GLA, antagonized by 375 μg/kg atipamezole. Induction was smooth, ranged from x̄ ± SD = 2.8 ± 0.6 to 4.3 ± 1.8 min, and did not differ significantly between protocols, species, or sex. In NBA, immobilization time ranged from 43.8 ± 27.8 to 66.5 ± 40.0 min and did not differ between protocols or sex. Muscle relaxation was judged to be better with K/X and K/M versus T/Z. In GLA, the response to the anesthetic protocols was more variable and immobilization time ranged from 30.4 ± 6.2 to 98.4 ± 33.7 min. The main difference was observed in GLA females receiving the T/Z combination, in which immobilization time was significantly longer versus males, but also versus GLA K/M group, and versus NBA T/Z group. Effects on body temperature, heart rate and respiratory rate were limited. Thirty six to 50% of the individuals showed hypoxemia (S_pO₂ < 85%) through-out anesthesia and values <80% also were recorded but the hypoxemia was not associated with clinical signs. With T/Z and K/X, recovery was irregular and prolonged up to 2 to 3 hr in some individuals. In K/M groups, first standing was observed 1.0 to 16.4 min after i.m. atipamezole injection without adverse effects. Finally, the three anesthetic combinations used in this study were effective and safe agents for 30 to 40 min immobilizations including minor surgery procedures. The ability to antagonize the medetomidine-induced sedation with atipamezole significantly reduces the recovery time, making the K/M combination preferable, especially in field conditions.