Mobile telephones were used to collect data on the relationship between gambling and mood state from gamblers in the field. Seventeen gamblers called an interactive voice response system running on a computer before, during and after a gambling episode. Measures taken in this way included self-reports of anxiety/arousal, the amount of money gambled, whether the result was a win or loss, the amount won or lost, and the type of gambling engaged in. Other measures were taken during an initial briefing session using conventional questionnaires that included self-reports of anxiety/arousal taken in a non-gambling situation, dissociation during gambling, and a measure of degree of impairment of control. The results showed that subjective anxiety/arousal levels were significantly higher during and after gambling than during the urge to gamble or at baselines. Losing was associated with increased subjective anxiety/arousal after play, and winning was associated with a decrease in subjective anxiety/arousal. This suggests that gambling may be a cause of increased subjective anxiety/arousal, rather than functioning to relieve it. A cluster of variables associated with impaired control and subjective anxiety/arousal levels was also identified. The method of collecting data using mobile telephones appears to be a valuable development.