The register of experiences and information through memory is crucial for the expression and adaptation of future behaviors. The use of psychotropic substances, a practice that has accompanied human history, can alter various cognitive functions. This chapter discusses the impact of drug use on memory in humans, with an emphasis on working memory and explicit episodic long-term memory. Initially, we address the neuropsychological models that categorize types of memory and present the processes of acquisition, consolidation, and retrieval of long-term memories. We explore how the acute use can induce transient changes, while the chronic use induces neuroadaptations in the brain which can enduringly alter different types and processes of memory. We highlight factors such as heavy use pattern and early age of onset, which increase the likelihood and magnitude of neuropsychological alterations. We also discuss the bidirectional, and not necessarily causal, relationship between drug use and changes in mnemonic functions. Finally, we select the most socially relevant drugs (alcohol, cannabis, cocaine/crack, and opioids) and review scientific studies on the effects of their acute and chronic use, emphasizing the importance of understanding these effects to optimize the treatment of subjects with problematic substance use.