Therαstructure of thietane has been obtained from its previously measured dipolar couplings. The molecular geometry can be described by a model of hindered pseudorotation characterized by a double minimum potential function. The optimized values for the geometric parameters are:rCH= 1·077 Å, HCαH = 109·7°, HCβH = 108·8° and -6·8° for the bending coordinate. The puckering amplitudeqcorresponding to the potential minimum is 0·24Å, but the height of the inversion barrier (δV) cannot be determined because the surface σ(q, δV) for the root mean square (RMS) deviations between observed and calculated dipolar couplings shows a valley of minimum deviation instead of local minima.