Two hundred and thirty seven chemicals were tested to determine their effect on the germination ofOrobanche aegyptiacaandStrigahermontheca. From their activity in these tests and a knowledge of their general properties the following are regarded as being the most promising for the pre-em. control of (1)Orobanche— oryzalin, dichlobenil, chlorthiamid, nitralin and chloramben. (2)Striga— 2, 4-D, MCPA and a range of other phenoxy compounds, chlorfenac, with MON 097, prynachlor, PH 40–21, PRB-8, RU 12068 and U 27658 showing the most interesting activity among the newer compounds.