This usage-based study tests the explanatory power of an iconically motivated theory of lexical class. The principle that basic level gram matical categories are motivated by our direct perceptual experience is an integral part of Cognitive Grammar (Langacker 1987, Talmy 2000. However, recent research on English, Dutch, and German (Glynn 2006(Glynn , 2007 has revealed mixed results in the application of this theory, suggesting that its de scriptive power may be restricted to a very abstract level of semantic structure. This investigation focuses on the above question, looking at the class-lexeme productivity of a range of relational classes, such as adverbs and adjectives, in a more morphologically rich language. The lexical field is that of 'rain'-'snow' for the West Slavic language Polish. This perceptually based concept should offer a best-case scenario for examining the lexical compositionality with an iconically motivated grammatical category. Despite this, the results show no particular evidence for iconic motivation, throwing weight behind the position that iconic motivation in grammar is at best an abstract ten dency with little semantic impact.