Mimosa tenuiflora is a shrub/tree found in northeastern Brazil sometimes eaten by livestock and believed to be responsible for malformations observed in many animals from that region. The teratogenic compounds in M. tenuif lora are not known. This study used pregnant rats fed M. tenuif lora and components therefrom for bioassay and fractionation of possible teratogenic compounds. Rat pups were examined for cranial−facial defects and skeletal malformations. Experimental diets included M. tenuif lora leaf and seed material, extracts of leaf and seed, alkaloid extracts of leaf and seed, and N-methyltryptamine and N,N-dimethyltryptamine. Pups from mothers who received M. tenuif lora plant material, methanol extracts, alkaloid extracts, and purified N-methyltryptamines had a higher incidence of soft tissue cleft palate and skeletal malformations. Results are summarized as to the frequency of observed cleft palate and other noted malformations for each diet versus control.