Ten biphenylhydrazinecarboxylates were obtained by the condensation of o-biphenylhydrazine with alkyl chloroformates. The miticidal and insecticidal activities of the new compounds were evaluated against Tetranychus urticae and Sogatodes orizicola. Structure-activity relationships for the screened compounds are discussed. Some of the compounds displayed greater activity than did the commercial standards, propargite and carbofuran.