We report for the first time investigations on electroless plated-nickel phosphorus alloy (Ni) contacts to undoped amorphous silicon (a-Si:H). I-V characteristics of electroless NiP were compared with those of Nickel deposited by thermal evaporation. It was found that as-deposited NiP makes a rectifying contact to undoped a-Si:H. The effects of plasma annealing on the contacts were studied. NiP contacts on low pressure chemical vapour deposited a-Si are also reported here. © 1994.