The effects of the root-knot nematode (Meloidogyne incognita) on cotton plant-water relations were investigated. Cotton plants differing in their susceptibility to nematode infection were exposed to a water stress, and the resulting influence on plant growth and water relations measured. Plants of a susceptible cultivar (Stoneville 506) and a resistant cultivar (Auburn 634) were grown in pots in a growth chamber. Half the plants were inoculated with M. incognita eggs three weeks after planting, and measurements of various morphological and physiological parameters made 2 and 4 weeks later following a water stress period. Both nematodes and water stress had no significant effects on plant height, leaf area, or root length. Water stress and nematode inoculation significantly decreased the pressure-induced water flow through roots of both cultivars. No cultivar x nematode interaction occurred, although a trend was apparent for the flux of S-506 to be decreased more than that of A-634. While nematodes did decrease root hydraulic conductivity, this was not reflected in post-stress measurements of transpiration, stomatal resistance, leaf temperature, or components of leaf water potential.