[en] Basing on the examples from studies on the effect of ionizing radiation and ethylmethylsulphonate (EMS), 1.2-Dibromoethane (DBE) or NaF on the somatic mutation frequencies in Tradescantia different patterns of the interaction between chemical mutagens and ionizing radiation in inducing somatic mutations were shown. In the case of EMS or DBE and radiation a synergistic interaction was demonstrated. In the case of fluoride its influence on the DNA repair processes might be involved in the effects observed. All results are in good agreement with the predictions made by Chadwick and Leenhouts. 10 refs., 9 figs. (author)