Diquat was tested to determine its suitability for use as a preharvest desiccant of selected vegetable seed crops during 1997 and 1998. In separate studies, diquat was applied at 0,0.56, or 1.12 kg·ha-1 ai. to spinach (Spinacia oleracea L.), table beet (Beta vulgaris L.), and coriander (Coriandrum sativum L.) plants at usual swathing time. Except for beet seed in 1998, there was no clear trend toward reduced seed weight with increasing diquat rate. Spinach seed germination in 1998 and coriander seed germination in 1997 were reduced by diquat at 1.12 kg·ha-1 compared to seed from nontreated plants or plants treated with 0.56 kg·ha-1. In all crops, diquat at 0.56 kg·ha-1 was adequate for crop desiccation purposes. However, seed producers should consider the potential benefits from chemical desiccation that may potentially lower germination of the harvested seed. Chemical name used: 6,7-dihydrodipyrido[1,2-α:2′,1′-c]pyrazinediium ion (diquat).