This work presents the development of a probiotic dried apple snack consisting of dried apple cubes impregnated with Lactobacillus casei NRRL B-442. Apple cubes were impregnated with probiotic microorganisms and dried under different temperatures (10-60 degrees C), with or without application of ultrasound. The viability of Lactobacillus casei in the dried apple snack was evaluated studying the effects of drying conditions and ultrasound application (as a drying enhancing technology). A mathematical model was developed to predict the drying kinetics and the inactivation of Lactobacillus casei. Drying and microorganism inactivation rates increased with increasing process temperature and with ultrasound application. The concentration of probiotics in the apple snacks was similar to the concentration of microorganisms in commercial probiotic dairy products when the apples were dried at 60 degrees C or when ultrasound-assisted air-drying was applied, thus proving that the production of dried probiotic apple snacks is possible and technically viable.