Only a small proportion of people with a substance use disorder (SUD) receive treatment. The shortage of SUD treatment providers, particularly in rural areas, is an important driver of this treatment gap. Telemedicine could be a means of expanding access to treatment. However, several key regulatory and reimbursement barriers to greater use of telemedicine for SUD (tele-SUD) exist, and both Congress and the states are considering or have recently passed legislation to address them. To inform these efforts, we describe how tele-SUD is being used. Using claims data for 2010-17 from a large commercial insurer, we identified characteristics of tele-SUD users and examined how tele-SUD is being used in conjunction with in-person SUD care. Despite a rapid increase in tele-SUD over the study period, we found low use rates overall, particularly relative to the growth in telemental health. Tele-SUD is primarily used to complement in-person care and is disproportionately used by those with relatively severe SUD. Given the severity of the opioid epidemic, low rates of tele-SUD use represent a missed opportunity. As tele-SUD becomes more available, it will be important to monitor closely which tele-SUD delivery models are being used and their impact on access and outcomes.