Trials were conducted in the three-year period 1987-89 at the Experiment Centre of the Department of Agronomy and Agro-Ecosystem Managment, Pisa University, situated at Torretta, San Piero a Grado (P1). In an experimental randomized block design with 5 replications, 15 treatments of chemical weedkilling made up of active compunds singly or in mixtures, intended for distribution at crop pre-cmcrgence, with the exception of lmazametabenz applied at post-emergence, were compared each year with the control. At the site on which the experiments took place, the tested pre-emergence compounds showed in general a good herbicide efficacy; Fluorchloridone, the mixure Oxyfluorfen + Alachlor, which appeared however slightly phytotoxic, and those obtained by adding Metha-benzthiazuron or Metobromuron or Linuron to Pendimethalin, were seen to be particualrly actlve. Concerning the achene yield, in the first two experiment years the treatments which gave the best results were Fluorchloridone and Methabenzthiazuron + Pendimethalin: Whereas in 1989 the best results were given by the mixtures Alachlor + Linuron, Oxadiazon + Metolachlor and Pendimethalin * Linuron.