Because our knowledge of the skeleton in hylids is so incomplete, we are not attempting to place _Smilisca_ in the general scheme of hylid phylogeny on the basis of skeletal characters. Instead, our purposes are to describe the skeleton and its ontogenetic development in one member of the genus (_S. baudini_), and to make comparisons that show taxonomic differences in osteological characters among species of _Smilisca_. The study of 68 dried skeletons and 25 cleared and stained preparations, including an ontogenetic series of _S. baudini_, has resulted in an understanding of the progressive development of skeletal elements and a knowledge of interspecific and intraspecific variation in these elements. Furthermore, investigations of the osteology have provided correlations between some cranial characters and certain aspects of external morphology. _Descriptive Osteology of Smilisca baudini_ The following description is based primarily on an adult female (KU 68184): _Skull._--The skull is large, solid, and broader than long; the greatest width is between the sutures of quadratojugal and maxillary on either side of the skull (Pls. 2-3). The maxillaries bear well-developed dorsal flanges, curve gently, join the moderately convex premaxillaries anteriorly and form a slightly truncate snout. The combined premaxillary width is about one-fourth the width of the skull. The premaxillaries are separated medially, and laterally from the maxillaries by sutures. Each premaxillary bears a dorsomedial alary process, which is anteriorly convex and four times as high as the depth of the lateral wing of premaxillary; each premaxillary also has a ventromedial palatine process that projects dorsally from the lingual edge of the premaxillary. The septomaxillaries are closely associated dorsally with the premaxillaries immediately lateral to the prenasal processes.