Insights from previous karst studies of the relatively simple and stable carbonate islands of the Caribbean and Western Atlantic have been applied to develop the carbonate island karst model (CIKM), a general model with which we can interpret the karst of more complicated islands in the Western Pacific. This paper summarizes the karst of the five southernmost Mariana Islands in order of increasing complexity. All exhibit complicated histories of tectonic uplift and subsidence overprinted by glacio-eustasy. Each, however, is distinct and can be described in total or by subunit in terms of the four idealized carbonate island types defined in the CIKM: (1) simple carbonate island, (2) carbonate-cover island, (3) composite island, and (4) complex island. Aguijan is a simple carbonate island, but contains a probable phreatic-lift cave draining a confined aquifer. Tinian illustrates application of the CIKM to subunits: the northern lowland is a simple carbonate island area, while the southeastern ridge fits the carbonate-cover island category, and the central portion fits the composite island category. Rota is a composite island grading laterally from the volcanic core into a carbonate-cover island, thence to a simple carbonate island from the southwestern highland to the plains and terraces north and east. Northern Guam is a simple carbonate island ringing a carbonate-cover section, which contains a small composite island portion. Southern Guam exhibits composite and complex island features. Saipan is a complex island, where syndepositional volcaniclastic units interfingering with limestone are faulted to create isolated aquifers, including confined aquifers drained by phreatic-lift caves.