We investigate educational assortative mating, or homogamy, by modelling the hazard of entry to first marriage for a sample of residents of Great Britain. Using marital, and imputed educational, life-histories drawn from the British Household Panel Study, we estimate first a set of competing-risk models where the outcome variable is defined as respectively hypogamy, homogamy and hypergamy. Age, educational participation and cohort have very strong effects, in directions that may be expected. Time gap between leaving education and marrying shows some signs of the hypothesised effect (that a greater time-lag means less homogamy). Cohort differences suggest men are decreasingly likely to marry down and women decreasingly likely to marry up. We also fit a second set of competing-risk models, where the outcomes are marriage to individuals of specific educational levels. We argue that these are more stable models, and that they provide more insight into the actual marriage patterns. In both sets of models we attempt to control for the changing opportunity structure by including estimates of the educational distribution of single people in an appropriate age range. While this is obviously a necessary control variable, and while it has strong effects on other covariates, its own parameter estimates are hard to interpret. We cannot therefore claim that the effect of changing marginal distributions has been fully removed, but we feel our estimates are nonetheless improved.