Testing human hair for drugs of abuse is a relatively new technique which requires control before being fully accepted in Justice applications. A consensus procedure was recently proposed to the four French Laboratories performing hair analysis for opiates and cocaine. Results of two independent controls have shown that the laboratories have performed very well quantitatively, using the recommended method. In order to compare these results with those obtained by other procedures, one sample was sent to 15 laboratories concerned with the analysis of human hair for drugs of abuse in Germany, Italy, Spain, and United States. Results from this study have indicated that the French recommended method is in accordance with the general procedures.