This article describes a new method for calculating and verifying the tension loads of hanger cables, which are used in the construction of cable-stayed, suspension, and arch bridges. The technique employs a laser vibrometer to measure the frequency of the cable’s vibration. The article describes older methods for measuring tension forces in cable elements and their drawbacks. The new technique requires a small area on or off the bridge for the operator and his equipment, and does not disrupt traffic. The new method gets the best results when the laser’s beam can hit the cable at a point that is between one-third the cable’s length and its midpoint.