The aim of this study was to determine the individual and combined toxic effects of Kyleo herbicide (160 g/l 2,4-D; 240 g/l glyphosate) and lead acetate on the development of chicken embryos. The chicken eggs were dipped in the solution or emulsion of the test materials for 30 minutes before starting of incubation. The applied concentration of lead acetate was 0.01% and of herbicide Kyleo was 1%. The treatments were performed on day 0 of incubation, and the embryos were examined on day 19 by the followings: rate of embryo mortality, body weight, type of developmental anomalies by macroscopic examination. The body weight was evaluated statistically by one-way ANOVA with Tukey and Dunnett post-test, the mortality of embryo and the developmental anomalies were analysed by Fisher test. Lead acetate alone and in combination with herbicide significantly reduced the body weight of the embryos but statistically increased the mortality of embryo. Single and concomitant administration of lead acetate increased the rate of embryo mortality. Developmental abnormalities were observed sporadically due to the single and simultaneous administration of the test items. Based on the results there is a possibly additive toxic interaction between the lead acetate and Kyleo that can highly reduce the viability of the embryos or can lead to extinction of wild birds.