We look at an important application of Z-Fuzzy Relation (ZFR) [5,6] in medical diagnosis. The objective of the paper is, we wish to construct an appropriate mathematical model utilising Z-Fuzzy Subset (ZFS) which can be implemented as a computer aided medical diagnosis system. Here additionally, reliability of data has to be taken into account and z-fuzzy relationship between symptoms and diagnosis has been found with ultimate accurate reliability solutions and also, these generalizations are substantiated with numerical example.