An experimental study of the effect of solvents on the rate and product selectivity of the solvated Diels−Alder reaction between cyclopentadiene and methyl acrylate is presented. The experiments were carried out in concentrated solution rather than the dilute solution used in previous studies by other workers. Gas chromatography and in situ Fourier transform infrared spectrophotometry were used to analyse the concentrated model reaction in the solvents, methanol and n-hexane. Reaction rates at 20 °C were 5 times faster, and the ratio of endo to exo adducts was initially 2.5 times greater in methanol. However, while the second-order rate constant remained approximately constant over the duration of the reaction, the selectivity for endo product in methanol dropped as the concentration of the products in solution increased. The origins of these effects are discussed in terms of solvent parameters, as are the implications for solvent selection.