Experimental studies have been carried out to evaluate the effects of carbaryl (l.-naphthyl-methyl-carbamate)- an anticholinesterase pesticide - on the morphogenesis and development of the chick embryo. A solution containing 0.5 mg of carbaryl has been injected in the allantoic sac of the embryos treated (n = 130), at the 5th or 6th incubation day. In comparison with a control group (= 70), some morphological alterations have been found in the embryos treated, at the expense of the skeleton apparatus, particularly in the most distal portions of the lower limbs, as tibial and metatarsal angulations, with their curtailment. Such effects might be related to an interference in the synthesis of NAD (nicotinamide-adenine-dinucleotide), as reported for other organophosphoric pesticides.