AbstractNMR spectral data are given for the A‐ring in ten 4‐en‐3‐one steroids, and the strategy of the spectral analysis is described. The data are interpreted in terms of an equilibrium between normal and inverted half‐chair conformations, with the normal conformation predominant in all cases except when 2β‐acetoxy substitution forces inversion. Substitution at the 17α position has no measurable effect upon the A‐ring conformation while 6α and 19‐nor substitution have only a small effect. Unsaturation at the C‐5 position results in a flattened A‐ring. The results obtained from NMR are compared with those obtained by x‐ray crystallography. The A‐ring conformation shows far less variation in solution