The first participatory or inter-active science centre in Australia was Questacon, which operated in Canberra for the eight years, 1980-1988. Its very success lead to its demise: it became the inspiration for the National Science and Technology Centre which opened in late 1988. Questacon, in common with many of the World's new breed of science centres and museums, was modelled on San Francisco's famous Exploratorium. These new institutions have copied ideas and even actual exhibits from the Exploratorium, but most of them have failed to copy the Exploratorium's use of Explainers, a feature which Exploratorium staff think is integral to the whole concept. Questacon is one of the institutions in which an explainer system was established, although it differed in some significant respects from that at the Exploratorium. Participatory science centres have been seen as part of the answer to the problem of increasing public awareness and understanding of science. There is a growing body of literature which is concerned with the learning of science in informal educational settings, such as in these centres, but there has been very little work done on the role of museum docents or their equivalents in this learning. One study of the Exploratorium's Explainers concentrated on the value of their work as explainers for the people involved in the system, in terms of their own personal development. The aim of the present study was to compare the two explainer systems and to investigate the work of Questacon Explainers both in terms of their own personal development and in their interaction with visitors to the centre.