In a method of guiding a missile in flight to a target (FIG. 1), the location of the missile and the range to the target are measured at a plurality of moments during the flight of the missile (step 10). The location of the target is calculated from the measured ranges and the measured missile locations (step 20). A required velocity vector angle is calculated from the calculated location of the target and a guidance law (step 30). A lateral acceleration required to provide the missile with a velocity oriented to the target at the required velocity vector angle is calculated for the missile (step 40). The missile is caused to accelerate with the calculated lateral acceleration, so that the missile to follows a trajectory according to the guidance law (step 50).