The first NMR observation of the planar zigzag conformation (beta-form) in a poly[(R)-3-hydroxybutyrate] uniaxially oriented film with high tensile strength is reported. A C-13 two-dimensional (2D) off-magic-angle spinning NMR method which directly correlates the peak positions with the molecular orientation in uniaxially oriented samples was used. The 2D NMR spectra provide the C-13 carbonyl signal of beta-form separately from that of the 2/1 helix conformation (alpha-form). The orientations of the carbonyl carbons for alpha-form and beta-form were determind and compared to the previously proposed molecular models.