Abstract
Thet eratogenic activity of several disazo dyes during rat embryogenesis has been investigated by Wilson (1955). In addition to the marked teratogenicity of trypan blue Wilson also demonstrated that Evans blue was moderately active and that Niagara blue 4B and Niagara sky blue 6B were possibly active. On the other hand, several other closely related disazo dyes such as Congo red and azo blue were found to cause no malformations in the surviving offspring.