A theory of urban park values is presented using the theory of island biogeography as an analogue. The theory predicts that two factorsothe size of park and distance from concentrated human habitationoinfluence the diversity of park values. The theory posits the diversity of human values for parks will increase with park size while the diversity of park values will decrease further from concentrated areas of human habitation. Spatial data from a study of Anchorage, Alaska, residents indicate a relatively strong relationship between park size and the diversity of park values and a weak, inverse relationship between distance from domicile and diversity of park values. The implications of the theory for urban area park planning are discussed.