Using crystalline hen's ovalbumin, an experiment on passive Schulz-Dale reaction in guinea pigs was done. The results are as follows: 1). After 24 hours of incubation period, the minimal sensitizing dose of antiserum which would cause passive Schulz-Dale reaction in guinea pigs is 0.5 unit per 1 ml guinea pig blood. 2). As the dose of sensitizing antibody increases, the dose of antigen lessons, but the critical dose depends upon the individual animal. Furthermore no definite propotional relation exists between the two. 3). The minimal antigen dose on minimal sensitzing antibody dose is the binding zone equivalent dose by Ogata's method or the 1/4 of it. 4). The most appropriate antigen dose to cause anaphylaxis to the isolated guinea pig intestine which is passively sensitized is the binding zone equivalent dose of the antibody used in this reaction. 5). Comparing bovine serum which is complex antigen and crystalline hen's ovalbumin which is simple antigen, the minimal antibody sensitizing dose is extermely small in quantity in the latter when in passive Shulz-Dale reaction.