Abstract: In a cellular mobile communications network, routing decisions pertaining to supplementary services are made by a home location register (HLR). For calling subscriber supplementary services, such as private numbering plans, a mobile services switching center (MSC) requests that the HLR perform the necessary routing decisions, and the HLR responds accordingly. For called subscriber supplementary services, such as call forwarding on busy, the MSC sends status information (such as the busy condition) to the HLR, and the HLR responds by determining supplementary call routing information, which is then sent to the MSC. Determining the supplementary call routing information may require that the HLR select from among several routing alternatives, in dependence on a condition such as time-of-day.