The present paper presents a brief account of the nature and formation of categories. It also reports on some of the findings obtained by investigating the way native speakers of Brazilian Portuguese and American English organize their semantic categories. Eleven semantic categories taken from the Battig and Montague (1969) category response norms were used in the study. The way the Brazilians and the Americans behave, in ranking the various category members is statistically analyzed by assessing levels of agreement within and between groups. The results of the analysis indicate that, although, there exists some correspondence in the way the two groups behave in ranking and in describing functions and attributes associated with category members, culturally specific constraints also exist and these will influence ranking decisions. Additionally, subjects? performance suggests that categorization behaviors appear to be motivated by two broad approaches to category structure: a prototypical approach based on feature overlap and a schema-directed approach based on instantiations prompted by the individual?s world knowledge.