In the present work, the variations in the solids circulation rate and solids holdup were analyzed to study the behavior of a liquid-solid circulating fluidized-bed (LSCFB) regime. The results confirm the existence of two regions in the regime of LSCFB. A new concept of critical liquid velocity, j(lc), is proposed in the present work for demarcation between region I and region 2, which is found to be a constant value of about 1.3 u(t) for all particles considered. The operating range of the LSCFB regime is obtained for the various particles and a correlation is developed from the data to estimate the maximum total liquid velocity. The predicted maximum liquid velocity was compared with the experimental values and found to be in good agreement within +/- 9%. The effects of total liquid velocity, particle size and density on the stable operating range are discussed. Analysis of the experimental results shows that stable operation prevails both in region 1 and region 2.