A series of studies of likelihood of adopting risk-reducing or weight-reduction activities revealed that the perceived difficulty of adoption was a more powerful factor in likelihood of adoption than was a perceived effectiveness of the activities. This finding is significant because most intervention programs emphasize convincing clients of the effectiveness of their methods and treat difficulty as a given or a constant. These studies showed not only that difficulty varied, but also that the relationship between likelihood of adopting an activity and the perceived effectiveness and difficulty of the activity was multiplicative and, therefore, curvilinear. At low levels of difficulty, likelihood of adoption was high, but as difficulty increased, likelihood dropped rapidly. The relationship between effectiveness and likelihood, on the other hand, showed small increases in likelihood as effectiveness increased to moderate levels, with little increase at higher levels. These relationships were more pronounced among those for whom the target risk was highly relevant. One implication for practice is that a greater payoff will be realized by reversing the conventional focus of intervention and instead helping clients reduce the difficulty of adopting necessary activities.