Oil shale retort runs 028 (16% void) and 029 (7% void), composed of competent shale blocks plus shale rubble, were completed. Retort 028, processed with air at a flux of 0.017 kg/sub air//m/sup 2/ /sub shale/.second, had peak temperatures of 700/sup 0/C, a retorting rate of 1.1 m/day, and a yield of 82% FA. Retort 029, processed with air at a flux of 0.027 kg/sub air//m/sup 2//sub shale/.second, had peak temperatures of 750/sup 0/C, a retorting rate of 1.6 m/day, and a yield of 75% FA. Comparisons of retort model calculations with experimental data from previous retort run 027 (16% void, air flux of .029 kg/sub air//m/sup 2//sub shale/.second were good; observed experimental yield was 95% FA, calculated yield, 92.8%; experimental retorting rates varied from 9.5 to 8.9 cm/h, calculated rates from 10.3 to 10.0 cm/h; observed local heating rates ranged from 29 to 14/sup 0/C/h, calculated heating rates from 20 to 16/sup 0/C/h; and observed peak temperatures ranged from 815 to 825/sup 0/C, calculated from 820 to 825/sup 0/C.