Debate surrounding the effectiveness, or otherwise, of marine reserves has not been well informed by data. However, in areas where marine reserves have been established for some time, valuable information is now becoming available. New Zealand's no-take marine reserves have demonstrated large increases in abundance and size of exploited species such as Snapper Pagrus auratus, Spiny Lobster Jasus edwardsii and Blue Cod Parapercis colias in marine reserves. Significant increases have been rapid, occurring within one year in the case of snapper, but only evident where full no-take protection is afforded. These increases in biomass of exploited species translate into levels of egg production between 4.4 and 18 times those of surrounding areas of coastline. There is no evidence of increased egg production translating into increased recruitment to fished populations, but such effects would be impossible to detect given the small proportions of coastline protected in reserves. There is some evidence that, in marine reserves, benthic soft bottom communities have responded to protection from direct effects of fishing such as trawling and dredging. More surprising have been the indirect responses of benthic reef communities to protection from fishing. Recovery of predators such as P. auratus and J. edwardsii has allowed urchin-dominated barrens areas to revert to more highly productive kelp forests. In this way reserves have allowed us novel insights into ecosystem function as well as the pervasiveness of indirect fishing effects. New Zealand reserves offer no direct evidence of the often-touted spillover-related enhancement of fisheries yield. However, they also show that reserves do not “lock up” fisheries resources and at least for J. edwardsii, CPUE (Catch Per Unit Effort), yield and costs are just the same adjacent to a reserve area as in open fishing areas nearby. Thus both conservation goals are achieved at no cost to the fishery. Despite advances in fisheries management structures in New Zealand, such as the Quota Management System, significant uncertainty remains about levels of stock abundance and catch rates. This is true even for New Zealand's best-studied stocks, such as P. auratus. Given that even the best fisheries management systems remain demonstrably less than perfect, it seems reasonable to try and guarantee some minimum level of stock abundance by putting in place marine reserves. On balance there is ample evidence to show that positive outcomes can be provided by reserves, and little or no support for suggestions that reserves will have negative effects for both conservation and fisheries.