The New Zealand Worker Representation and Participation Survey, drawing on earlier surveys in the USA and Britain, charts the incidence, location and nature of demand for union membership in New Zealand for the first time. Using Freeman and Roger™s (1999) definition, we estimate the ‘representation gap™, the extent of unsatisfied demand for union membership, at 17.8 percent of the labour force. The gap is greater among younger and lower paid workers in smaller organizations in private sector service industries. How much of the gap consists of workers who would definitely join a union if actually offered the opportunity is a debatable point. New Zealand unions face three major challenges: indifference on the part of the majority of workers in non-unionized firms, lack of union reach (mainly into small, private sector workplaces), and free-riding. These challenges imply a mix of responses in union strategy and public policy.