Patulin is a toxin produced by a number of different moulds such as Penicillium and Aspergillus. It can be found in damaged or mouldy fruits, particularly apples. If contaminated apples are used to make juices, high levels of patulin are likely to be carried through to the final product. Toxicity of patulin is connected with its affinity for sulphydryl groups of biological molecules causing harmful effects in human and animal tissues. Hence, the present work was aimed to evaluate the possible teratogenic effect of patulin (0.002mg /kg b. wt/day for 35 successive days) through the application of dominant lethal gene test on the albino rats. The animals were classified into 4 main groups each group included 12 mature rats (3 males and 9 virgin females): Group1(rats were received distilled water, control); group2 (all males were received patulin); group3(all females were received patulin) and group4 (all males and females were received patulin). At the end of the experiment, each 3 of females were caged with 1 male (in each group) for mating. The results of the present work indicated that, patulin was maternal toxic, embryotoxic and significantly induced dominant lethal gene.