Human dietary intake and excretion of polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs), and biphenyls (PCBs)--collectively referred to as dioxin-like compounds (DLCs)--were investigated. Two groups of seven subjects were studied during 1999 and 2000: one aged 23.9 +/- 4.5 years, the other aged 49.4 +/- 5.2 years. For each subject, two week-long experiments were held. In one, omnivorous diets were administered, whilst in the other, a vegan diet was studied. While exposures via the omnivorous diets exceeded those via the vegan diet on a sigmaWHO-TEQ basis; for some subjects sigmaPCB exposures were comparable in both diets, implying that plant-based foods can make an appreciable contribution to exposure to sigmaPCB. For all subjects, the average dietary exposure during the omnivorous trial to PCDD/Fs and PCBs combined (expressed as WHO-TEQ) was--at 1.09 pg kg(-1) bw d(-1)--lower than recent UK "food-basket" estimates. For the same diet, the average sigmaPCB exposure for all subjects was--at 5.01 microg person(-1) d(-1)--higher than recent UK "food-basket" estimates, but consistent with recent estimates for other industrialised countries. Net absorption/excretion but not faecal excretion rates of DLCs were related to dietary intakes. Furthermore, excretion rates of the most persistent DLCs--i.e. PCB #s 138, 153, and 1,2,3,6,7,8-HxCDD--were statistically significantly greater for the older subjects. Combined, these data imply that excretion rate is dependent on body burden, and that the majority of DLCs in human faeces arise from endogenous excretion.