The transesterification reaction of ethyl phenylacetate to hexyl phenylacetate on an "imprinted" silica catalyst of the type first reported by Heilmann and Maier is investigated. In the presence of sulfuric acid co-catalysts, the data obtained here reveal that catalytic activity can be due to phosphorous species leached into solution; no evidence for molecular recognition and catalysis from an imprinted site in the silica is observed. In the absence of co-catalysts, no conclusion regarding the presence of an imprinted site in the silica can be ascertained because of the low level of activity relative to background autocatalysis.