The bovine H1-receptor DNA was transfected into Chinese hamster ovary cells (CHO-K1) using an expression vector. Binding studies revealed very high expression levels of the receptor which was found to have a Kd for [3H]-mepyramine of 1 nM. Addition of histamine resulted in a concentration-dependent increase in intracellular calcium which was found to involve both release from intracellular stores and entry across the plasma membrane. Furthermore, the response demonstrated the pharmacological characteristics of an H1-receptor-mediated event. Thus, we present the first report of the high, functional expression of the bovine H1-receptor coupled to mobilisation of intracellular calcium in CHO-K1 cells.