Antibiotics are chemical compounds which produced by microorganisms (especially produced by fungi) or produced synthetically which able to kill or inhibit the development of bacteria and other organisms. F.G Troches® is classified as antibiotic. This study aims to determine the relationship of the knowledge level towards the rationality in using F.G Troches® as antibiotics. This type of research uses cross-sectional analytical design. Sampling was taken by purposive sampling technique. Analysis of the result used the chi-square test with a 95% confidence level or α = 0.05. The results showed that there was no significant relationship between the level of knowledge towards the rationality of using F.G Troches® as an antibiotic (p <0.213). It is concluded that whether good or not good the person's knowledge level in treatment by using F.G Troches® doesn't affect the rationality.