The paper reports one of the first ever studies to evaluate the effectiveness of an online help and guidance service for problem gamblers. The evaluation utilised a mixed methods design in order to examine both primary and secondary data relating to the client experience. In addition, the researchers posed as problem gamblers in order to obtain first-hand experience of how the service works in practice. A total of 80 participants completed an online evaluation questionnaire, and secondary data were gathered from 413 distinct clients who contacted an advisor. It was concluded that the service appears to be one of the few genuinely international guidance and "counselling" services available to problem gamblers. Gambling online was the most preferred form of gambling and gambling location of "GamAid" clients. The service also appears to be favoured by females more than any other comparable service. Overall, the vast majority of clients were very positive about their experience of using "GamAid," although there were some minor technical difficulties. In light of the findings, the utility of using online guidance and therapeutic services is discussed. (Contains 5 tables and 1 note.) [This study was funded by the Responsibility in Gambling Trust (RiGT).]