Little research has been conducted in Ukraine since the 1990s to understand the organization of drug market and its implications for people who inject drugs (PWID). In this study, we explore how PWID perceive the retail drug market in a large Ukrainian city. Qualitative data were obtained during in-depth interviews and analyses included open coding, coding tree development and revision, axial coding, and identification of higher-level domains. Participants’ narratives focused on types and forms of drugs available, perceptions about drug quality, methods of buying drugs, and the relationships that are formed and maintained by participating in the drug economy. The described technical organization of the drug market, with multiple contingent combinations of drug types, forms and means of obtaining drugs (hand-to-hand vs stash-based) resulted from diversification and digitalization of the retail injection drug market. The social organization of the drug market in the form of relationships with sellers and drug use partners represented the response to the fundamental problem of uncertainty. The lens of “transaction cost” helps explain strategies PWID used to manage uncertainties, including finding reliable and suitable sellers, sending money and picking up the stash under the threat of being stiffed or caught by the police, choosing the product itself, using the intermediaries to outsource risky operations and forming groups to procure and inject together. Our results indicate that the technical and social organization of drug distribution in Ukraine stimulates formation and continuation of relationships and impacts the choices of what, how, and when to inject beyond individual preferences. The policy and practice implications include the need to monitor and understand the retail drug market to develop and deliver more efficient and client-oriented services, incorporate and leverage social networks structure for information sharing and behavior change, pilot and implement drug testing services to assist with management of uncertainties.Copyright © 2020 Elsevier B.V. All rights reserved.