Field trials were conducted over three years at Samaru in the northern Guinea savannah ecological zone of Nigeria to evaluate the performance of 20 improved cowpea varieties under conditions of natural infestation by a parasitic weed, Alectra vogelii (Benth.). Grain yield ranged from 695 to 2043 kg ha-1.The best yielding varieties were IT95K-1072-57 and IT97K-499-35. These varieties also hosted very low number of Alectra shoots, suggesting that they are resistant to it. In addition to high grain yield, both varieties produced high fodder yield, making them to be dual purpose varieties. They are therefore ideal for the semi-arid zone where livestock production is an integral part of the farming system and Alectra is a major constraint to the attainment of high cowpea yield. Alectra did not emerge on two of the varieties (IT95K-1090-12 and IT97K-818-35), indicating that they are highly resistant to the weed, but these varieties were among the poorest yielders. They may, however, be good sources of Alectra resistance in cowpea breeding programmes. Four varieties, IT95K-1380, IT93K-273-2-1, IT95K-222-5 and IT93K-573-5 supported high number of Alectra shoots and were therefore highly susceptible to its parasitism.
