Type-3 fuzzyType-3 fuzzy logicFuzzy logic (T3FL) and fractal theory (FT) and their use in medical diagnosisMedical diagnosis have been put forward in this book. The focus is on the essential reasons for employing type-3 in achieving an accurate medical diagnosis. Type-3 is a new theory to model uncertaintyUncertainty that can be employed in diagnosis. Type-2 has been previously employed as a way for dealing with medical diagnosis, but recently type-3 offers an alternative in dealing with more complex medical problems. In this work, we briefly review the theory of type-3, which could be studied in a more profound way. Additionally, we postulate a way for building type-3 fuzzy-fractal systems in medical diagnosisMedical diagnosis