We systematically reviewed the health and social science literature on access to and use of information technologies by homeless persons by searching 5 bibliographic databases. Articles were included if they were in English, represented original research, appeared in peer-reviewed publications, and addressed our research questions. Sixteen articles met our inclusion criteria. We found that mobile phone ownership ranged from 44% to 62%; computer ownership, from 24% to 40%; computer access and use, from 47% to 55%; and Internet use, from 19% to 84%. Homeless persons used technologies for a range of purposes, some of which were health related. Many homeless persons had access to information technologies, suggesting possible health benefits to developing programs that link homeless persons to health care through mobile phones and the Internet.