The teratogenic effects of three herbicides (Flubalex, Fusilade S and Maloran 50 WP) were studied in chicken embryos. Each of the three test substances was administered on days 0 and 12 of incubation. Treatment was followed by evaluation on day 19. The compounds were injected into the air-chamber of eggs at three different concentrations. The medium concentration corresponded to that usually applied in chemical plant protection. In order to determine the combined toxicity of the three herbicides, the medium concentration of Maloran 50 WP and three different concentrations of Flubalex of Fusilade S each were administered simultaneously at a final volume of 0.1 ml per egg, at similar times. Evaluation was done on day 19. In tests of individual toxicity, after injection on day 0 of incubation Maloran 50 WP and Flubalex caused a significant reduction in body mass, while Maloran 50 WP and Fusilade S resulted in marked embryonic mortality. After injection on day 12, the medium and the highest concentration of Flubalex and the highest concentration of Fusilade S caused a marked increase in embryonic mortality. The developmental anomalies were of sporadic nature: their incidence increased only after Flubalex treatment, irrespective of the time of administration. The combined administration of Maloran 50 WP and Flubalex on day 0 resulted in a significant or marked body mass reduction in all groups. Embryonic mortality increased substantially after treatment with the highest dose of Flubalex, while all three concentrations of the other two herbicides led to similar results. When treatment was performed on day 12, the two highest concentrations of Flubalex and the highest concentration of Fusilade S caused expressed embryonic mortality. The developmental anomalies did not show a dose-dependent effect in any of the test series.