The effect of several herbicides on exudation of carbon compounds from 14C-labelled conidia of Cochliobolus sativus was studied using a model system that imposes fungistasis. Ungerminated conidia were incubated on a bed of sand through which herbicides in a sterile, dilute salts solution were percolated for 3 h. Atrazine (10 p.p.m.), linuron (10 p.p.m.), trifluralin (24 p.p.m.), MCPA (800 p.p.m.), and paraquat (100 p.p.m.) increased exudation of labelled compounds from conidia by as much as 31%, 27%, 69% 220% and 237%, respectively, over the basal exudation rate. None of the herbicides at the concentrations used had any effect on subsequent germination of the conidia.