Basten M, et al. - Considering the significance of the insights in sexual risk behaviour trajectories of MSM in assessing starting points for the timing of HIV prevention methods, researchers studied longitudinal trajectories of sexual risk behaviour predictive of HIV acquisition from sexual debut onwards. They developed a comprehensive behavioural risk score predictive of HIV seroconversion and on the basis of this risk score, they estimated linear trajectories of sexual risk behaviour and MSM group membership. They identified 3 trajectories of sexual risk behaviour: Low risk (90.3% of the sample), Falling high risk (6.5%) and Rising high risk (3.3%). During follow-up, a higher risk of acquiring HIV was noted among MSM following the Falling high risk (20.5%) and Rising high risk (25.0%) trajectories. The Falling high risk trajectory was noted to be associated with younger age at sexual debut, fewer steady partnerships and high percentages of substance use. A correlation of the Rising high-risk trajectory was noted with increasing percentages of substance use over time.