Experiences with Marine Reserves (no-take Marine Protected Areas) in New Zealand and internationally are reviewed. Reserves became popular with the public and provided economic benefits. In one reserve, ‘spill-over’ of lobsters counter-balanced lost fishing. The reserves provided the controls that showed the effects of fishing on ecosystems through depleted populations and habitat change due to trophic cascades. Studies in other countries indicated that these trophic cascades were common globally. Research has shown that reserves protect benthic and pelagic species, including those that move outside the reserves. Marine Reserves can provide benefits to (1) conservation of species and habitats, (2) science as controls for fishing effects, and (3) fisheries as reference sites that conserve natural genetic and population structure, host brood-stock, and provide spill-over to nearby fisheries. They should be distributed geographically in networks that include replicated examples of habitats and species. To do so, they need to be suitably located, large enough, and enforced to fulfil these opportunities. However, these benefits remain limited by the relatively small area occupied by marine reserves within and between countries.