Most studies of peripheral interstitial fluid lipoprotein composition have been made on interstitial fluid-derived from skin and connective tissue. We developed techniques which allowed simultaneous comparison of lymph (a model of interstitial fluid) from skeletal muscle and skin in control (C) and cholesterol-fed (CF) dogs. Lipoprotein fractions were separated by ultracentrifugation. Skeletal muscle interstitial fluid HDL concentrations were approximately twice those of skin. However, the concentration of VLDL-LDL particles was similar in both interstitial spaces. HDL particles from both microvascular beds showed evidence of extensive remodelling when compared to plasma HDL from the same animal. Relative to apo A-I, skeletal muscle HDL was enriched in free cholesterol and apo E (C and CF dogs) and apo A-IV (CF dogs). Skin-derived HDL was consistently enriched in free cholesterol, apo E and A-IV in both C and CF dogs. These studies indicate that similar remodeling of plasma HDL occurs in widely different tissues which together constitute approximately 70% of the total interstitial space. The relatively high concentration of plasma-derived and remodeled HDL within the interstitial space of skeletal muscle is consistent with that tissue's importance in reverse cholesterol transport.