The purpose of this study was to determine the reliability of eccentric and concentric strength of adults with cerebral palsy (CP) as measured on the Kin-Corn. Fourteen subjects performed four eccentric and concentric contractions of shoulder adduction and abduction, and knee flexion and extension at a speed of 60°/s during three testing sessions. Peak and average torque were calculated for each type of contraction for each of the four movements. Generalizability coefficients were high for all scores (r = .79 to .96) except average eccentric extension of the knee (r = .26). The variance components revealed that differences between test sessions were large (8.5%–65.8%) compared to the differences between trials (0.0%–5.8%). These data indicate that the Kin-Corn is a reliable mode for testing average and maximal concentric muscular strength, and maximal eccentric contractions on adults with CP, following an initial orientation session.