Abstract: A method of leak testing at least one "main" cavity (1) formed in a body (2), involving filling the main cavity with a test gas (6) at a determined pressure (PO). The leakage pressure variation (15, 16) in the main cavity is measured while reducing the pressure inside the main cavity in steps (dp.sub.n) by means of a controllable valve (12). The various values of leakage pressure variation, are compared with equal values being representative of a part that is leaky and with values that become smaller from one measurement to another being representative of the presence of at least one secondary cavity communicating with the main cavity via a seepage path (4) having high head loss. The two cavities taken together are possibly non-leaky.