The objective of this paper is to determine whether the flow regimes in spouted beds can be recognized by the mutual information function of pressure fluctuation signals. Differential pressure fluctuation time series were obtained in a gas spouted bed of 0.12-m i.d. at different axial and radial positions, with glass beads and silica gel particles. It was found that the packed bed has a low level and fast decay rate of mutual information, suggesting a quite random signal. Unstable spouting exhibits a high level of mutual information and strong periodic motion. While for a stable spouting regime, the level of mutual information and the decay rate around time zero are between those for the packed bed and unstable spouting regimes. The mutual information function for signals measured on the wall has higher predictabilities compared to those measured inside the bed. The determination of optimum time delay by the aid of the first minimum of the mutual information function was discussed. It has been found that the first minimum of the mutual information function can be used as the optimum time delay if it does exist. In the case that no first minimum exists in the mutual information function, the suggestion of Daw and Halow (Daw, C. S.; Halow, J. S. AIChE Symp. Ser. 1993, 89, 103-122) that 10-50% of the maximum value of the mutual information resulted in too small a time delay. An appropriate time delay can be determined by comparing the similarity between phase space trajectories and pseudo phase space trajectories.