Substituted paraconic acids in the benzene and naphthalene series were prepared in a pure-white state. These wore converted to the α-naphthols by heating under standard conditions and the yields of the naphthols compared with a view to determining the effects of substituonts on the ring-closure. Whilst the theory of steric influence satisfactorily predicts the effect of substituents on the ease of ring-closure in the benzene series, no postulate per se is sufficient to explain in entirety the observed facts arising from ring-closure of the compounds in the benzene and naphthalene series studied in these researches.