Experiments were carried out to determine the cholinergic properties of sensory neurons of the chick embryo by measuring the choline acetyltransferase activity (ChAT) and [3H]choline uptake. The choline acetyltransferase activity in the dorsal root ganglia of an 8-day-old chick embryo was 24.2 +/- 2.52, which increased to 45.4 +/- 9.69 pmol ACh/mg protein/min in the ganglia of 12-day-old embryos. Sensory neurons derived from dorsal root ganglia of 10-day-old embryos and maintained in a serum-free culture medium supplemented with insulin, transferrin and nerve growth factor (NGF) also contained significant amounts of ChAT (21.9 pmol ACh/mg protein/min). Omission of NGF resulted in neuronal death, and the enzyme activity could not be measured in these cultures. A specific inhibitor of ChAT, hydroxyethyl naphthylvinyl pyridine (NVP), when added to the assay mix produced a dose-dependent inhibition of ChAT from cultured neurons. Cultured sensory neurons incubated with [3H]choline followed by repeated washouts took up and retained [3H]choline. The uptake of [3H]choline was reduced by about 45% when NaCl, in the incubation medium, was replaced by LiCl. A specific inhibitor of choline uptake, hemicholinium-3, caused about 75% inhibition of [3H]choline uptake. It is implied that sensory neurons of the chick dorsal root ganglia express cholinergic properties during development.