This paper studies various reliability measures. Reliability measures are quantities used for analyzing reliability and maintenance models. Sometimes when the maintenance cost rate is minimized, the system reliability measures are so low that they are not acceptable in practice. The following instantaneous reliability measures are considered in this paper: instantaneous failure rate, instantaneous repair rate, instantaneous maintainability, instantaneous reliability and instantaneous availability. The explicit expression and numerical results for the instantaneous reliability measures are shown. Also, their relationships are shown.