Abstract: The present invention relates to method and to an apparatus for the non-destructive testing of spot welds and the determination of the diameter of a spot weld. The testing method comprises subjecting the welds (2) to a mechanical test using a pneumatic hammer and during the test the so-called "stuck" welds are destroyed. The remaining welds then undergo a punctiform inspection using a rheometric method. This method consists of creating a potential difference between the supply electrodes (10), of which there are even numbers in contact with the weld (2). Measuring electrodes (8) located in the vicinity of the supply electrodes make it possible to obtain a resulting quantity of the different voltages measured. After calibrating the resulting value of the voltages makes it possible to deduce therefrom the diameter of the weld and consequently its efficiency.Application to the determination of the diameter of a spot weld.