Biological exploration of México and Central America has revealed the presence of a diverse fauna, elements of which have undergone speciation in separate areas within the relatively small region. Some genera of amphibians, especially _Eleutherodactylus_ and _Hyla_, are represented by many species having small geographic ranges in México and Central America. Most of the species of _Hyla_ inhabiting the lowlands have been known to science for many years, and most of the novelties today are found in the less accessible highlands. No fewer than 19 new species of hylid frogs have been discovered and named from México and Central America in the past decade.

In the spring and summer of 1966 I studied hylid frogs in many parts of southern México and Central America; the field work was designed to obtain specimens and data that would resolve certain systematic problems. To a certain extent the studies were successful, but in the course of the work five previously unknown hylids were discovered; these are named and described in this paper. The only species described herein that I do not know in life is one of _Plectrohyla_ that has been represented in museum collections for several years but was not obtained in my own field work.

In this paper I am presenting diagnoses, descriptions, and brief comments on the relationships of five new species and one subspecies. More exhaustive accounts will be included in a monograph, now in preparation, on the Middle American hylids.