This is Part 1 of a study concerning the pedology of 11 soils of Puerto Rico which represent the range of highly weathered soils of this island. Six Oxisols, 4 Ultisols and 1 Inceptisol are discussed. The environmental conditions and profiles studied are described. Soil formation in response to pedogenetic factors is discussed in terms of accumulation of parent material and solum development. Particular emphasis is placed on soil-landscape relationships. The occurrence of Oxisols on Miocene, Pliocene and Pleistocene surfaces is ascribed to particular geomorphic conditions, ultrabasic rocks, and pre-weathered sediments, respectively. The Ultisols are mainly developed in saprolites on backslopes of geologically young surfaces. The Inceptisol is found on a strongly weathered regolith in a perhumid mountain region. In all soils studies, profound weathering was largely accomplished prior to rather than as part of pedogenic alterations. Clay illuviation cutans could not always be positively identified in the field and the results of thin-section studies did not conform with field observations in all instances. This suggests the need for a re-examination of the diagnostic value of argillans in soils with low-activity clays and, as a corollary, a re-evaluation of the definition and taxonomic role of the argillic horizon. The soils were classified according to the U.S. Soil Taxonomy, the legend for the FAO-Unesco Soil Map of the World, and the French soil classification system. The placement in taxa of these systems and their correlations are discussed. The correspondence of the Puerto Rican soils studied with those of other tropical areas is described.
