Information concerning the design and performance of various types of miniature internal combustion engines is presented. Comparisons are given for the performance of miniature and larger engines with means for extrapolating large engine practice into the miniature size range. Performance curves and design features of selected miniature test engines are presented and discussed. Desirable design features for various types of applications are given. A summary is presented of the fuel and lubricant characteristics necessary for miniature engines. This report describes a continuation of the earlier study presented in WADC-TR-53-180.