Self-managed superannuation funds (SMSFs) – small retirement savings funds with four or fewer members – now manage almost one third of retirement savings in Australia, and serve over one million members. The number of SMSFs has increased to more than half a million in two decades. Yet little is known about the reasons people start the funds and how they are operated. We combine survey responses of more than 500 SMSF members and 500 large superannuation fund members to understand the motivation of SMSF members and how they compare with similar people who stay with a large fund. Control over investments and tax minimisation are the most common reasons for starting a fund. Satisfaction with large funds and unwillingness to take on the administrative burden of self-management are the most common reasons for not doing so. SMSF members do not show more financial skill than non-members, but they do express a higher risk tolerance and a more trusting attitude to financial professionals. We present evidence that the majority of SMSF members start their funds at the suggestion of financial professionals. We also show that the types of people who say they are thinking about starting a SMSF are different in significant ways from the types of people who end up as SMSF members, further evidence for the influence of the advice industry.