Bioerosion - the removal of lithic substrate by the erosive activities of living organisms- has not previously been discussed for New Zealand shore platforms. This paper aims at drawing attention to bioerosion as a process active in shore platform development. Detailed reference is made to bioerosion occurring on the alternating sandstones and siltstones of the Waitemata Formation found outcropping on the coastline around Auckland. In this area several facets of shore platform morphology may be attributed to the direct effects of boring and browsing marine organisms. A classification of animals causing bioerosion, based on mechanism of erosion, is presented, and the geomorphic significance of the various groups discussed.