The authors calculated binary indicators of seven positive and 23 negative behaviours for 22,898 8th and 15,828 11th grade students who participated in the Oregon Healthy Teens Survey across two school years. Relationships among these variables, using both the Jaccard measure of co-occurrence and the relative risk for each member of each variable pair, given exposure to the other, showed strong inter-relationships within, but not between, the sets of behaviours. The likelihood of negative behaviours given negative behaviours was much stronger than the likelihood of positive behaviours given positive behaviours. Positive behaviours provided little protection against the likelihood of negative behaviors.