In response to widespread concern about illegal drug use and the assoc
iated risk of the spread of HIV/AIDS, a study was undertaken to examin
e whether it was, in principle, feasible to conduct a trial providing
heroin to dependent users in a controlled manner. Such a trial involve
s real ethical issues which are examined in this paper. The general is
sues examined are: should a trial be an experiment or an exercise in p
ublic policy%; acts and omissions; countermobilisation; termination of
a trial, and payment for drugs and for a trial. The specific issues e
xamined are: selection of trial participants; privacy; issues for staf
f working on a trial; coupling the trial with other treatment, and iss
ues for researchers. A number of alternative approaches to the various
ethical issues are presented and discussed.