Field trials of preventive regimens in Thailand and French Polynesia.

Field demonstration trials of preventive agents or methods are needed so that the effectiveness and acceptability of such methods can be evaluated when used as part of the prevailing system and life style in a particular community. Agents so tested should have already been shown in a clinical trial to have a positive effect. Field demonstration trials differ from clinical trials in having no traditional control group; the study is not 'blind'; there is no special supervision and there is no special selection of participants.