In greenhouse tests both butachlor and thiobencarb injured the rice (Oryza sativa L.) cultivars IR36 and Salumpikit. Depth of seeding altered the tolerance of both cultivars to the herbicides. Planting IR36 3 cm deep and Salumpikit 4 cm deep protected them from herbicide damage. Planting deeper than 4 cm generally resulted in smaller and lighter plants. Seed treatment with 1,8-naphthalic anhydride (NA) at 1% w/w further reduced the phytotoxic effect of the herbicides, especially at shallower planting depths. The plants from the NA-treated seeds were taller and heavier than those from the untreated seeds.