Fears of a crack 'epidemic' in the United Kingdom of the kind experienced in the United States remain unfounded. However, findings from an ongoing serial point HIV prevalence study indicate that the use and injection of crack cocaine among injecting drug users (IDUs) in London is on the increase. Data on patterns of drug use and drug injection were collected over 4 years (1990-93), from IDUs recruited from both drug treatment and community-based settings. All respondents were asked about their drug use in the 6-month period prior to interview. The use of crack cocaine increased significantly from 16% in 1990 to 59% in 1993 and the injection of crack cocaine from 1% to 27%, respectively. The findings suggest that crack cocaine is being injected more regularly, with increases over the 4-year period in those who reported injecting the drug at least once per week. In response this paper considers both the health implications of, and the treatment response to, the increasing use and injection of crack cocaine among IDUs in London.