Four δ Scuti stars (θ Tuc, ϱ Phe, 1 Mon and 21 Mon) have been observed intensively in an effort to understand the periodicities present in these stars. The stars selected were known to be of variable amplitude and relatively large light range. The data of each star was Fourier analysed. In no case did the period ratios have values consistent with the period ratios of low order radial modes. The most interesting result appears in the analysis of 1 Mon. The three principal periodicities present occur at P1 = 0.13612, P2 = 0.13378 and P3 = 0.13855 days. To within the errors these periods form an equal frequency split, i.e. 1/P2 −1/P1 = 1/P1 −1/P3.