ABSTRACT The subject of prop transport in vertical fractures has been much discussed in the literature in the past five years. Yet, there are many questions that remain unanswered. Probably the most difficult question to answer involves particle transport by cross-linked gels. The major problem encountered in studying particle settling in cross-linked fracturing fluids is the extremely slow settling velocities. This limits the type of experimental apparatus that can be used to closed systems with long particle residence times. The low settling velocities coupled with the difficulty of obtaining good rheological data makes the development of mathematical correlations for the data difficult. In this study, two different experimental models have been used to obtain particle settling data. One model consists of a parallel plate apparatus in which the shear on the fluid is provided by a moving belt and the other consists of a concentric cylinder device similar to that described by Novotny (SPE 6813). Both of these models are capable of providing adjustable shear rates and long particle residence time necessary for data collection. Data will be presented for both cross-linked and uncross-linked fluids. The viscosities and degree of cross-linking have been varied in order to detect the influence that cross-linking has on particle settling velocities over and above the contribution that cross-linking makes to the viscosity.