The studies included the progeny of 14 stallions and 115 mares of Purebred Arabian breed mating each other (totally 180 matings) in state breeding. The nervous balance of all horses (parentsand progeny) was evaluated using the excitability test by Budzyński’s method. The heart rate measured by telemetric apparatus was used as an additional index expressing the quality of nervous reactions. Statistically significant dependences between the level of nervous irritability of stallions and mares mating each other and the level of this trait in their progeny were stated. The possibility of predicting the level of progeny nervous irritability using the value of this trait in parents was shown. Significant dependences between points in the excitability test and the level of heart rate measured during ethological studies allow to use this index for the evaluation of horses` behavioral reactivity.