The purpose of this investigation was to characterize the contractile properties of individual slow- and fast-twitch myofibers from highly trained distance runners. Muscle biopsies were obtained from the gastrocnemius of eight competitive runners (RUN) and eight recreationally active individuals (REC). Slow-twitch (myosin heavy chain [MHC] I) and fast-twitch (MHC IIa) myofibers were isolated and analyzed for diameter (µm), peak force (P_o, mN)), contraction velocity (V_o, FL s^-1), and power. Maximum oxygen uptake was higher (P<0.05) in RUN (71±1 vs. 47±2 mlkg^-1min^-1). Diameter of MHC I and MHC IIa fibers from RUN subjects was ~20% greater (P<0.05) than REC. Peak force of the MHC IIa fibers was 31% higher (P<0.05) in RUN while P_o of MHC I fibers was not different between groups. No differences for specific tension (P_o/CSA) were present between groups for either fiber type. V_o was higher (P<0.05) in MHC I (+70%) and MHC IIa (+18%) fibers from RUN subjects. Peak absolute power (µN FL s^-1) of both fiber types was greater (P<0.05) in RUN (131 and 85% for MHC I and MHC IIa, respectively). Additionally, normalized power (W Liter^-1) of the MHC I fibers was 64% higher in RUN while no differences existed for normalized power of MHC IIa fibers. These data indicate that highly trained endurance runners have elevated contraction velocity in both slow- and fast-twitch myofibers. These characteristics of the fast-twitch muscle fibers have not been previously reported in competitive endurance athletes and may contribute to the high level of running performance in these athletes.