Decadron solution for injection contains Dexamethasone-21-phosphate disodium, phenol, creatine, sodium citrate, sodium bisulfite, and sodium hydroxide. Therefore, the question of which substance of these is really effective for inducing convulsion, was investigated using mice. The results of the present studies were as follows: 1) Sodium citrate is the only substance in the Decadron solution which induces a convulsive seizure, similar to the Decadron Convulsion. 2) Erection the tail and tachypnea were observed in mice after administration of dexamethasone-21-phosphate disodium, but no convulsive seizure was recognized by dexamethasone-21-phosphate disodium itself. 3) In the case of simultaneously administered sodium citrate and Dexamethasone-21-phosphate, a Decadron type of convulsive seizure was observed. Therefore it was suggested that dexamethasone played the roll of an activat or for the convulsive seizure.