Human interferon α1 (HuIFN αl) is known to protect bovine as well as human cells against viral infection. Hence, we investigated the specificity and tissue distribution of receptors for HuIFN al on various cells. [35S]HuIFN αl bound specifically to homogenates of bovine tissues and particularly to bovine liver, but there was also specific binding to spleen, kidney, brain, adrenal gland, lung, thymus, skeletal muscle, heart, mammary gland and testis. There was no difference in the degree of binding of HuIFN a to foetal or adult liver. Competitive binding experiments showed that bovine interferon aC (BoIFN αC) competed with HuIFN α1 for binding to a bovine liver plasma membrane preparatjgn, indicating that these two IFNs bind to the same receptor. An 35S-labelled IFN α1-receptor complex was isolated from bovine liver extracts by SDS/polyacrylamide gel electrophoresis, and shown to have a molecular weight of 153 kDa. Isolation of the bovine IFN α receptor would be a feasible approach to the characterization of the HbIFN α receptor. © 1990 Informa UK Ltd All rights reserved: reproduction in whole or part not permitted.