This paper investigates the nature of frequencies in the Nagoya Interlanguage Corpus English of spatial prepositions of AT, ON and IN. The proportions and ratios of these three prepositions, because of their grammatical characteristic, are to an extent fixed not only for native speakers but also advanced non-native speakers. The analysis is divided into three parts: a general examination of overusage and underusage of these forms, an examination of the most distinctive words in contrast to AT, ON and IN, and an examination of the distinctiveness in native speaker and non-native speaker corpora separately. The results show that 1) while there is a general tendency to underuse these forms by non-native speakers their overall proportions and ratios remain stable; 2) fluctuations occur mainly with lexical words; 3) fluctuations in AT, ON and IN may be topic driven but a minor factor as their fixed nature is governed by grammatical and communicative needs. Proportional usages of AT, ON and IN though stable show internal variations (polysemy). Non-native speakers are inclined to produce native-like proportions but miscue in their literal and metaphorical usages. The findings suggest further research into the ratios of literal to metaphorical usages is required.