This application relates to methods and apparatus for temperature monitoring for integrated circuits, and in particular to temperature monitoring using a locked-loop circuits, e.g. FLLs, PLLs or DLLs. According to embodiments a locked-loop circuit (200, 600) includes a controlled signal timing module (201, 601), wherein the timing properties of an output signal (SOUT, SFB) are dependent on a value of a control signal and on temperature. A controller (201, 601) compares a feedback signal (SFB) output from the timing module to a reference signal (SREF) and generates a control signal (SC) to maintain a desired timing relationship. A temperature monitor (202) monitors temperature based on the value of the control signal. For FLLs and PLLs the signal timing module may be a controlled oscillator (201).