This Brief Communication investigates laminar Craya-Curtet flows, formed when a jet with moderately large Reynolds number discharges into a coaxial ducted flow of much larger radius. It is seen that the Craya-Curtet number, Cϭ(J c /J j ) 1/2 , defined as the square root of the ratio of the momentum flux of the coflowing stream to that of the central jet, arises as the single governing parameter when the boundary-layer approximation is used to describe the resulting steady slender jet. The numerical integrations show that for C above a critical value C c the resulting streamlines remain aligned with the axis, while for CϽC c the entrainment demands of the jet cannot be satisfied by the coflow, and a toroidal recirculation region forms. The critical Craya-Curtet number is determined for both uniform and parabolic coflow, yielding C c ϭ0.65 and C c ϭ0.77, respectively. The streamlines determined numerically are compared with those obtained experimentally by flow visualizations, yielding good agreement in the resulting flow structure and also in the value of Confined jet flows are of interest for many practical engineering applications. The configuration shown in Fig. 1, in which an axisymmetric jet of radius a, with Ӷ1, discharges into a coaxial ducted stream of radius a, is relevant in particular to ejector systems and combustion chambers. Most of the previous works have been devoted to the case of turbulent flows, corresponding to the high-Reynolds-number jets most often encountered in applications. Of particular relevance are the pioneering experimental and theoretical analyses of Craya and Curtet 1 and Curtet, 2 which addressed as a central issue the emergence of regions of reverse flow near the confining wall when sufficiently weak coflow is present. A dimensionless parameter based on similarity considerations was proposed to characterize the resulting flow, similar to that previously proposed by Thring and Newby in their study of turbulent, coflow diffusion flames, 3 for which the recirculating flow provides a key stabilizing mechanism. For the case of uniform coflow investigated by Craya and Curtet, their parameter reduces to Cϭ(J c /J j ) 1/2 in the limit →0 of small inner jet radius, where J c and J j represent the momentum fluxes of the coflow and of the jet, respectively. A detailed account of experimental results, theoretical analyses and approximate integral solutions for turbulent CrayaCurtet jets can be found in Ref. 4. Unlike the above mentioned studies, we address here the laminar flow arising for values of the jet Reynolds number R j ϭ͓J j /()͔ 1/2 /ӷ1 below a certain critical value, when the resulting symmetric solution remains steady, giving a slender jet of characteristic length R j a that can be described with relative errors of order R j Ϫ2 with the boundary-layer ͑BL͒ approximation. The same incompressible fluid of density and kinematic viscosity is assumed to be present in both streams. In the analysis, the ratio of the inner to the outer radii will be assumed to be very small, as done...