The universe of syringe services programs (SSP) across U.S. Territories and Tribal Nations was created by merging datasets maintained by the North American Syringe Exchange Network (NASEN) and RTI, including: · SSPs in NASEN’s directory of known SSPs in the U.S., its territories, and Tribal Nations · SSPs in NASEN’s directory that do not wish to be publicly listed but have agreed to be contacted for research purposes · SSPs that belong to NASEN’s Buyer’s Club that are not part of the directory · SSPs that are not in NASEN’s directory and do not participate in the Buyer’s Club, but are known to NASEN · SSPs that have responded to prior RTI Arnold Ventures Surveys of SSPs that are not included in the NASEN directory · SSPs proactively identified through SSP networks by the study team and partners (e.g., state health department websites, state networks, regional conferences, partner organization networks).