Apparatus for the detection and measurement of small amounts of deuterium in small-sized samples by the photoneutron reaction is described. With a 25-Ci24Na gamma-ray source, a net response of 7 counts/ min per microgram of deuterium in sample sizes from 0.1 to 1.0 ml is obtained. The lower detection limit in such samples is ~1.7µg of deuterium, or the amount in 0.05 ml of natural water.