It is the first and important practice for the study of the psychotropic drugs to observe the spontaneous movement of animals. Although many methods have been known for measuring the spontaneous movements, most of them are to find the change of motor activity of a single animal. Many investigators reported the automatic measurement of the motor activity. Photoelectric method was first used by Siegel et al. (1), which was improved by Dews et al. (2) in mice. Takagi et al. (3) traced the spontaneous movement of a mouse using a modified photoelectric apparatus. The central nervous system stimulant effect of 2-dimethylaminoethanol (DMAE) was first reported by Pfeiffer et al. (4) and had been confirmed by Konigsmark et al. (5), Himwich (6) and Brown and Gangloff (7). It was also confirmed by clinical trials. Pfeiffer et al. (8) proposed the hypothesis that DMAE played the role of a precursor of acetylcholine in the central nervous system. Groth et al. (9) found that DMAE was incorporated in the mouse brain more rapidly than choline and probably converted to brain choline. However, Pepeu et al. (10) and Kiplinger et al. (11) had different views from that of Pfeiffer. In this paper, we have developed a method of recording the spontaneous activity of grouped mice, in order to take an accurate measurement of a little change of motor activity by drugs. We investigated the effect of DMAE and its acyl esters on the spontaneous movement of the grouped and/or individual mice.