The glass transition temperature of the interphase was tailored to investigate its influence on micromechanical behavior. Three different types of experiments were carried out on the samples with tailored interphases. First, interferometric measurements were made on samples consisting of a single 30 micron carbon fiber coated with a low Tg resin and embedded in an epoxy matrix. The resulting displacement profiles were compared with those of an uncoated fiber. Second, single fiber fragmentation tests were performed over a range of temperatures for samples consisting of 7 micron AS4 carbon fibers which were either coated with the same low Tg resin, a higher Tg resin or left uncoated. Finally, microcracking investigations were performed by subjecting a cluster of four fibers with tailored interphases to various thermal loads. The location and occurrence of microcracking were correlated with interphase Tg. Both the interferometric results and the single fiber fragmentation results supported the existence of an interphase with reduced glass transition temperature in uncoated samples. Interphase glass transition temperature had a significant effect on both load transfer and thermally induced microcracking observed in the experiments. Additionally, it was shown that the interphase can be tailored to either enhance or hinder the observed effects.