ALTHOUGH frogs of the family Leptodactylidae have a wide distribution in the tropics and subtropics of the Americas there is little published information concerning their life histories and modes of development. This paper extends and enlarges upon the information presented by Stejneger (1904), Schmidt (1920), and Orton (1951) on the reproduction and young of Leptodactylus albilabris (Giinther). The observations and collections were made in 1943 during service with the U. S. Army Air Forces at Ramey Air Force Base (then called Borinquen Field) in the northwestern corner (Punta Borinquen) of Puerto Rico about five miles north of the town of Aquadilla. The material studied came from the vicinity of Ramey Air Force Base. NESTS.-Stejneger (op. cit: 579) found the eggs of L. albilabris in "a compact ball of snowy foam of a somewhat gelatinous consistency" beneath a stone in the water of a small stream. Schmidt (op. cit.) discovered three foam-filled nests, one beneath a large stone at the edge of a creek, another underneath a stone on a hilltop where there was no water in the vicinity, and a third under a rotten log beside a pool of standing water. About 30 nests containing embryos and an almost equal number of empty nests (i.e., which contained neither eggs nor foam) were examined. These nests were typically subspherical cavities hollowed out of soft earth. They were about 3 cm. in depth and 6 cm. in greatest diameter. As was true of the nests observed by Schmidt, the walls were smooth with no markings to indicate the manner of excavation. When eggs were present, the nests were completely filled with egg-foam masses like that described by Stejneger. One of the nests containing eggs was located under a stone beside a small stream. Three others were found beneath fallen palm fronds and palm debris in a swampy area. The remainder were within a meter or two of the edge of a small pond (approximately 10 meters in diameter), the water level of which fluctuated considerably with variation in rainfall. The ne ts found beside this pond were of three types; covered by (a) vegetable debris, (b) stones, and (c) domes of earth. Only three nests of type b were found. Types a and c were in approximately equal numbers. Each nest of type b was situated five or more centimeters within the outer border of the zone of contact between the stone and the earth. The edges of such cavities were in dose contact with the stone and there was no indication of the route by which the adults emerged from th nest after the laying of the eggs. The nests of type c were seen externally merely as small rounded elevations of earth about a centimeter