We investigate nonlinear propagation in the presence of the optical Kerr effect by relying on a rigorous generalization of the standard parabolic equation that includes nonparaxial and vectorial terms. We show that, in the ͑1 1 1͒-D case, both soliton and propagation-invariant pattern solutions exist (while the standard hyperbolic-secant function is not a solution). © 2004 Optical Society of America OCIS codes: 190.0190, 190.3270, 190.5530. Monochromatic optical propagation in the presence of a refractive-index distribution n͑r͒ n 0 1 dn͑r͒ is usually described by the scalar parabolic equation. This is a by-product of the Helmholtz equationand the scalar parabolic equation is derived from Eq.(1) in the paraxial approximation. More precisely, after writing the electric f ield as E͑r, t͒ A͑r Ќ , z͒exp͑ikz 2 ivt͒, where v is the angular frequency, k ͑v͞c͒n 0 , and introducing d as a typical length scale of variations in n͑r͒, we assume that the parameter h ͑Dn͞n͒ ͑l͞d͒ , , 1, which expresses the smallness of the relative variation of the refractive index over a wavelength scale. Besides, if the f ield is initially (approximately) transversely polarized, we neglect its longitudinal component A z with respect to the transverse one A Ќ ͑r Ќ , z͒, and we can derive, using the slowly varying approximation, the standard scalar parabolic equation:We can then automatically satisfy the divergence equation = ? ͑eE͒ 0 (where e e 0 n 2 ) by using it to derive the (small) longitudinal component A z . If the smallness parameter h becomes comparable to 1, then the approach presented above, which represents only the lowest-order approximation in h, fails, and higher-order terms have to be added to account for nonparaxial contributions. The recent progress in nanotechnology and the possibility of fabricating optical structures with subwavelength features are compelling reasons for generalizing Eq. (2) to the nonparaxial regime. This can be done rigorously if, after splitting the f ield into a transverse and a longitudinal part, one is able to derive an equation for the transverse part alone to first order in ≠͞≠z that contains terms to all orders in h. This task was recently carried out in the general case (linear or nonlinear) of a tensorial refractive-index distribution, $ n ͑r͒, in a manner that fully preserved the vectorial nature of the problem.