To determine whether enteric flora contribute to glucosinolate metabolism in humans, we evaluated the effect of a standard preoperative bowel preparation on dithiocarbainate excretion after ingestion of glucosinolates from mature broccoli. To prepare glucosinolates, florets from ice-packed broccoli were cut and immediately boiled in a stearn- jacketed kettle (8 L water, 5 min). Florets were removed, the remaining liquid was reduced to about half its original volume (over 5 min) and was added back to the cooked florets, and the mixture was homogenized in a Waring Blender. Samples were taken for analysis and the homogenate was stored at -80 degrees C. Individual doses consisted of 112 g fresh weight broccoli in 182 mL, containing 100umol non-indole glucosinolates, 0.5 umol isothiocyanates and no residual myrosinase activity; glucoraphanin constituted 76. 1 % of the glucosinolates.