Since 2001, the NIST Multimodal Information Group has coordinated evaluations of Machine Translation (MT) technology through the Open Machine Translation evaluation series (OpenMT). The 2015 evaluation continued to push the boundaryof text-to-text MT technology, focusing on informal data genres, in particular online chat and sms text messages as well as conversational telephone speech. For the very first time, OpenMT 15 included an audio-to-text track. Participants at OpenMT 15 received training and development data to build their systems. Participants collected the evaluation data, locally processed it, and submitted the output to NIST for scoring and analysis. During the workshop, participants will discuss the systems and their results as well as the next challenges in MT.