This paper reports a controlled evaluation of the six-part BBC TV series "So You Want To Stop Smoking?" which aimed to give advice and encouragement to smokers who wanted to stop. In an experimental design, 134 cigarette smokers in two firms were shown either the first two programs in the series or a control film of the same length. Smokers in the former group were asked to watch the remaining four programs at home on their own television sets. Questionnaires were sent to participants four months and one year later, and claims of abstinence were validated biochemically. The results did not provide clear evidence that the BBC series was more effective in encouraging smokers to try to stop and helping them to succeed than the control film. For comparison with our own results, we also abstract some findings from an uncontrolled but larger-scale evaluation conducted by the BBC's research department.