The history of zoo animal welfare legislation extends back to 1876, and is often tied to general animal welfare regulations. As knowledge and societal values have changed, so have the focus of zoos and the regulations governing them. Today, the issues involved in zoo animal welfare are complex and broad-based. Building on the basic welfare tenets of adequate feed, water, shelter, sanitation and veterinary care, current issues include the following: handling and training of captive animals, psychological well-being and environmental enrichment, enclosure design, species preservation, environmental and conservation issues, captive-breeding programmes. Complicating the matter further, government regulations try to assimilate all aspects of zoo animal welfare into the laws to provide humane care and handling for all species concerned. Zoo animal welfare will remain a challenging area, as increasing demands are placed on zoos and regulatory agencies to manage this diminishing resource.