OBJECTIVE The study aimed to examine the ability of prebiotic concentrations to increase the growth of probiotic bacteria in vitro. METHODS The probiotics used were Lactobacillus acidophilus and garlic (Allium sativum) extract. RESULTS The results showed that garlic can increase the growth of L. acidophilus bacteria with the lowest concentration of 4% being the most effective (p<0.05). Increased fructooligosaccharide (FOS) content in garlic can increase the significant growth of L. acidophilus as a probiotic bacterium. CONCLUSIONS The results showed that garlic can increase the growth of L. acidophilus bacteria by a minimum of 4% (p<0.05). Adding FOS to garlic can increase the significant growth of L. acidophilus as a probiotic bacterium.