Table 1 shows a comparison of enzyme activity converting purine nucleosides to purine bases between Labre powder and Labre-in- chocolate after treatment with simulated digestive juice. Control experiments were carried out after treatment with 085x NaCI in- stead of simulated digestive juice. Reactions were camied out with 2 mM guanosine and 4 mM inosine as substrates. In the reaction with Labre powder after treated 2 h with 0.85% NaCl, generations of 0.208 mM guanine and 0.489 mM hypoxanthine derived from de- composition of the substrates were observed after the reaction, but chocola no generations of guanine and hypoxanthine were observed in the reaction with Labre powder treated by simulated digestive juice 2 h. On the other hand, in the reaction with Labre-in-chocolate treated 2 h with 0.85 Naci, generations of 0.446 mM guanine and 1.316 mM hypoxanthine were observed, and generations of 0.320 mM guanine and 0.838 mM hypoxanthine were observed in the reaction with Labre-in-chocolate treated 2 h with simulated di gestive juice. These results showed that Labre-in-chocolate retained the enzyme activity in 0.85x Naci and also in simulated digestive juice, indicating that chocolate processing is useful to stabilize the enzyme activity in probiotics during gastric acid treatment