Abstract: Two principles for progressing from the precontemplation stage of change to the action stage were discovered. The strong principle states that progression from precontemplation to action is a function of approximately a 1 standard deviation increase in the pros of a health behavior change. The weak principle states that progression from precontemplation to action is a function of approximately a 1/2 standard deviation decrease in the cons of a health behavior change. In Study 1, these principles were derived from cross-sectional data on 12 problem behaviors relating the pros and cons of changing to the stages of change. In Study 2, these principles were validated on cross-sectional data from an independent sample of 1,466 smokers. Discussion focuses on the implications of these principles for individual psychology and public health policy.