Previous researchers on the semantics of spatial relational terms have reported the importance of geometric factors (e.g., Bennett. 1975; Talmy, 1983), the importance of functional factors {e.g., Coventry, Carmichael, and Garrod, 1994; Vandeloise, 1991), and the lack of importance of the nature of the Figure, or object located (e.g., Landau and Stecker, 1990; Talmy, 1983). In this paper, we present the results of an experiment testing each of these claims for the English spatial prepositions IN and ON. Our findings confirm that geometric and functional factors are indeed important. In addition, our results suggest that the nature of the Figure contributes to the selection of spatial prepositions.