A principal factor analysis was performed on 25 traits of eight varieties and strains of sunflower (Hellanthus annuus L.) grown in replicated field plots at one location in the State of Tamaulipas, Mexico in 1990. Drought was created by terminating irrigation through vegetative to seed filling stage. Factors representing patterns ofvariables interpreted as yield, harvest index, escape and storage were extracted. These factors were identified with the source and sink conslructs ofcrop physiologists. lt is suggested that the development of higheryielding sunflowers underwaterstress must be based upon rapid phenological development combined with â long reproductive pcriod, heavy stems at anthesis and the ability to translocate those assimilates to seed dcvelopment; this could be achieved by producing a heavy biomass at maturity and a high plant and head growing rates.