Zone circulating flow-injection analysis (ZCFIA) is a method for multi-detection of a sample zone injected into a closed-flow system formed by connecting the two ports of a single FIA manifold. Using an FIA instrument assembled with a multi-step pump, detection was carried out at various flow-rates. Subsequent analysis of the damped curves yielded a great deal of information concerning the theory of FIA. The data thus obtained were arranged to clarify correlations among general residence time, flow-rate, length and inner diameter of the reactor, sample volume injected and dispersion coefficient. As a result, several shortcomings and errors in FIA theory were discovered. Several qualitative formulations, containing variables suitable for the various conditions involved, were established and six qualitative conclusions were drawn.