In the years 1997 and 1998 effects of weed on the sexual indices of spiders (Araneae) were carried out during field tests with transgenic, herbicide tolerant sugar beet and maize crops. Because of the tolerance of the plants and the possible late application, different weed cover was determined in treatments. Catching was done with pitfall traps. Conventional fields of the same crops were used with a minimum distance of 500m from the testing site. With exception of O. apicatus (Blackwall) the catching of the males were higher than that of the females and the juveniles. No indirect effects of weed couldn't be determined on the species with exception of P. microphthalmum (O.P.-Cambridge) in both cultures maize and sugar beet.