This article reviews studies on the use of deception in psychological research, indicates other directions that such investigations might take, and suggests solutions to the problems posed by this tactic. Deception is widely used, but its efficacy is rarely evaluated. Subjects' suspicion is a useful index of effectiveness, and the only aspect that has been investigated so far. Many subjects may be suspicious of the deceptions in a study. This disbelief can be triggered by the experiment itself, operating in conjunction with the subjects' characteristics. Suspicion can affect the level of experimental performance or interact with it. The problems connected with this methodology may be minimized by improving the design of deception studies, by routinely assessing the effectiveness of the dissimulations, and by modifying data analyses.