Soil incorporation and site of uptake of preemergence herbicides was investigated under greenhouse conditions using green foxtail (Setaria viridis (L.) Beauv.) and the herbicides 2-chloro-4-ethylamino-6-isopropylamino-s-triazine (atrazine), 2-chloro-N-isopropylacetanilide (hereinafter referred to as CP31393), 3-amino-2,5-dichlorobenzoic acid (amiben), 3-(3,4-dichlorophenyl)-l-methoxy-l-methylurea (linuron), ethyl N,N-dipropylthiolcarbamate (EPTC), and [alpha],[alpha],[alpha]-trifluroro-2,6-dinitro-N,N-dipropyl-p-toluidine (trifluralin). As depth of incorporation of most herbicides was increased, control of green foxtail decreased, indicating a dilution effect. Subsurface application of herbicides at a 2-in depth generally was less than half as effective as surface application or shallow incorporation. With 3 different moisture conditions, shallow incorporation of trifluralin to depth of 1 in was beneficial at all moisture levels. Shallow incorporation of atrazine and EPTC improved effectiveness under conditions analagous to furrow irrigation but not under conditions simulating moderate or high rainfall immediately after application. Shallow incorporation of the ammonium salt of amiben increased effectiveness significantly under high moisture but decreased effectiveness under low moisture. Effectiveness of linuron was reduced by incorporation under moderate and high moisture. Shallow incorporation did not significantly affect results with CP31393 under any moisture condition. For the 6 herbicides tested, the expression of lethal action on tops of green foxtail was evident when herbicide was placed in the shoot zone but not when placed in the root zone during the 2-week period after seeding.