In this paper, gradient selected (gs) NMR experiments are presented for editing the proton, and two-dimensional (2D) H-1-C-13-correlation spectra of different fractions of the petroleum according to the carbon multiplicity. The state of the art experiments allow the much sought after simplification and resolution of the proton, and 2D H-1-C-13 correlated NMR spectra of such fractions in considerably reduced acquisition times. The proton-edited experiments offer a new and much convenient way of unambiguous estimation of cut-off points between signals from alpha-methyl and alpha-methylene protons in H-1 NMR spectra of petroleum fractions. The gs edited 2D H-1-C-13 correlated spectra of the fractions provide carbon multiplicity information and hetero-nuclear correlation with improved sensitivity in a single experiment leading to complete spectral assignment. These experiments have been applied to complex petroleum fractions for the first time, and show lot of potential to resolve various hitherto unanswered issues concerning the interpretation of the complex NMR spectra of the petroleum products. (C) 2002 Elsevier Science Ltd. All rights reserved.