Techniques for allocating transmission gaps and making cell measurements in asynchronous communication networks are described. A terminal establishes communication with a first communication network (e.g., a W-CDMA network), receives an initial allocation of transmission gaps for making cell measurements, and makes measurements for cells in a second communication network (e.g., a GSM network) during the allocated transmission gaps. The terminal determines the timing of at least one cell in the second network, which is asynchronous with the first network, and sends the cell timing to the first network. The terminal then receives a new allocation of transmission gaps for making cell measurements. The locations of the transmission gaps in the new allocation are determined based on the cell timing reported by the terminal. The terminal makes measurements for the at least one cell in the second network during the transmission gaps in the new allocation.