Seeds of eight species of Cruciferae were collected, usually in each of 3 years, and mixed with the top 7-5 cm of sterilised soil confined in cylinders sunk in the ground outdoors and cultivated three times yearly. The seedlings emerging were recorded for 5 yr and the numbers of viable seeds remaining then determined. Emergence of Alliaria petiolata was almost entirely restricted to February and March. That of Erysimum cheiranthoides, Lepidium campestre, Sinapis arvensis and Raphanus raphanistrum took place mainly in March and April, but seedlings continued to appear until late autumn. Some seedlings of Arabidopsis thaliana, Cardamine hirsuta and Sisymbrium officinale appeared in spring, but most did so in summer (C. hirsuta and S. officinale) or early autumn (A. thaliana). Seed survival in A. petiolata was of short duration and there were few seedlings after the second year, whereas 18% of the seeds of R. raphanistrum were still present and viable after 5 yr. Seed survival at this time for the other six species ranged from 1 -6% (C. hirsuta) to 6-1% (S. arvensis).