Mutagenic treatments were performed on F1 sunflower sceds with gamma rays (100 Gy, 200 Gy, 300Gy or 400 Gy dose) and with 0.2% ethyl methyl sulfonate. The screening for bifenox or glyphosate resistant progenies led to 18 M² homogeneous bifenox unaffected (resistant) progenies and 113 progenies segregating glyphosate partially resistant plants, respectively. The ratios of progeny numbers containing - bifenox homogeneous unaffected/segregant resistant plants,and -segregant partially resistant/homogeneously sensitive plants, suggested a mutational event towards a recessive allele.In the field, spraying with glyphosate appeared inefficient to study the mode of inheritance of the resistance. Therefore we developed an in vitro assay allowing us to investigate four progenies only segregating partially glyphosate resistant plants. About ten per cent of the individuals of these four progenies survived the in vitro assay while no control plant did. Glyphosate resistance was controlled for four generations of the progenies. The level of resistance against glyphosate was reproducible but low in vitro (10 ul Roundup/) or in field (360 g/ha) so that further work will be done to check a possible duplication of the EPSP synthase gene.