We apply a novel daily time series data set of daily turnover from one of Britain’s leading bookmakers to analyze potential substitution between lottery play and bookmaker betting. We find some evidence that bettors do substitute away from horse race, soccer and numbers betting when the effective price of lottery tickets is unusually low, that is, when there is a rollover or other special draw. This substitution has a highly specific pattern of timing that varies by sector. Our results further suggest that bettors rationally engage in forward-looking substitution within their betting portfolios