Polydrug use is viewed as an important public health issue since it has been linked, through research studies, to significant adverse health outcomes, such as drug overdose, increased risk of exposure to bloodborne pathogens, drug dependence, and decreased cognitive functioning. With the advent of club drugs, such as ketamine polydrug use has raised new health concerns. For purposes of this article, polydrug use refers to the drug combinations consumed by an individual during a single drug using event. This study describes polydrug using practices among a sample of 40 ketamine injectors, and examines particular drug using events, such as ketamine injection initiation, to describe the variability and risks involved in polydrug use within the sample. It highlights the sequencing of polydrug use, the forms of drugs consumed, and the modes of administrating drugs in the context of events that combined ketamine with one of six other drugs: marijuana, alcohol, heroin, speed, ecstasy, or hallucinogens. In describing polydrug using practices, the study consisted of 40 young ketamine injectors recruited from street and park settings in New York City. The findings indicate that young people typically use ketamine in the context of a polydrug using event, with polydrug using events being far from uniform. Specific drug combinations, such as ketamine and speed, may produce unique experiences that ultimately develop into a polydrug combination of choice. Tables, references