Based on size series of 12 larval Antigonia capros of 2.7 to 5.1 mm SL and 8 Zenopsis conchifer of 4.2 to 6.6 mm SL from the southwest Atlantic, ontogenetic development of both species is described. Head spination of A. capros revealed the same vertically directed spine formerly taken as diagnostic character for the related species A. rubescens. Myomere counts of 20 to 22 in the present material seem to be distinctive for A. capros compared to 25 myomeres of A. rubescens. The occurrence of A. capros larvae in the investigation area was restricted to austral autumn (April-June). The larvae were found in the tropical water of 23.9 to 26.0°C and 36.3 to 36.7‰ salinity over the outer continental shelf, north of 30°S. Z. conchifer larvae show a conspicuous uniformly brown colour all over, except for the tip of the notochord, which is transparent. Larval form is depressed, body depth of a 6.6 mm specimen is 46% of SL. The 5 rays of the pelvic fins are pigmented and reach beyond the anus. 33 to 34 myomeres are counted in the postlarvae. From 4.2 mm onward, occipital and postocular spines appear on the head of Z. conchifer, which distinguishes this species from the closely related Zeus faber. The larvae of Z. conchifer occurred from July through November in tropical and mixed water of temperatures between 17.5 and 23.4°C and salinities of 32.2 to 36.3‰. Larvae were found over the slope of the continental shelf and over deep oceanic waters as far south as 34°S. Reproduction of both A. capros and Z. conchifer in the southwest Atlantic is related to the tropical water of the southward flowing Brazil current. Z. conchifer has the wider range of occurrence into subtropical latitudes both a adult and as larvae, whereas A. capros is a typically tropical species reproducing north of latitude 30°S only.