Missed appointments create many problems in dental practices, as those patients who fail to turn up deprive other patients of an opportunity for treatment. This paper reports on a study of failures to attend appointments without giving advance notice in a NHS practice in the UK. A sample of 588 patients is analysed using Logit and Distribution Mixtures in order to devise policies to improve no-show rates. It is shown that a policy based on de-registration of patients who fail to attend an appointment would be justified on statistical grounds and would work in the long run, but that such policy would not improve things in the short run and can make them worse. The paper also discusses emergency treatment and workload at the practice.