Lloyd Bridges as Dr. Doug Standish

Brian Kelly as Dr. Craig Mosby

Shirley Eaton as Dr. Margaret E. 'Maggie' Hanford

David McCallum as Dr. Philip Volker

Keenan Wynn as Hank Stahl

Marshall Thompson as Dr. Orin Hillyard

Gary Merrill as Dr. August 'Gus' Boren

Ron Hayes as Brinkman

George Shibata as Prof. Uji Hamaru

Donald Linton as Vice President

Frank Logan as Captain of the Diligence

Don Wells as Sonar Man on the Dilligence

Celeste Yarnall as Secretary