The Edinburgh Study was a longitudinal research program that explored pathways into and out of offending among a single cohort of youth who began secondary school in Edinburgh in 1998. The study found a significant difference between boys and girls in levels of serious delinquency, but a relatively small difference in levels of delinquency in general, including minor as well as serious incidents. Delinquency increased sharply in sweeps one to three (ages 12 to 14), but then declined. The increase was greater among girls than boys, so the gender gap in offending was the narrowest around age 14, followed by an increase in boys' offending compared to girls. Delinquency that most often involved girls included thefts from home, writing graffiti, and truancy. Carrying a weapon, breaking into houses, robbery, theft from cars, and cruelty to animals were much more common among boys. The explanatory model for general delinquency was found to be much the same for boys and girls. The higher rates of general delinquency among boys compared to girls was due largely to situational opportunities, peer influence, and weakened social conditioning and moral beliefs. At age 15, boys remained significantly more likely to be involved in serious delinquency, even after taking into account 20 explanatory variables. This suggests that the difference in serious delinquency between boys and girls was due to a factor or factors not measured in the study. These findings are consistent with the theory that general delinquency tends to be limited to the period of adolescence; whereas, serious offending is more likely to persist throughout the life course, caused by deep-seated neuropsychological deficits more common in boys than girls. 4 tables, 10 figures, and 11 references