FIELD: physics. SUBSTANCE: method of searching for and identifying ionising radiation sources using ionisation counters or scintillation detectors moved on the search territory (zone), involving continuous measurement of the mean speed of counting the additive mixture of a signal and a background n(t) as the detecting system moves on the investigated territory; processing the obtained measurement information by breaking the vector n(t) into exposure time sections texp, the duration of each of which is equal and is preferably (8-15)·ts; determining the mean speed of counting the background b, the amplitude of the assumed signal am, and the position of the signal tm on the time scale; further calculating a parameter η using the formula where ts is the effective duration of the signal; comparing η with a threshold q0, which is determined from given false alarm probability; and making a decision on detecting the sought object if η>q0, wherein the obtained measurement information is processed by successively increasing the effective duration of the signal ts (1.3±0.1) times from the minimum ts1=4-t∂, then ts2=6·t∂, ts3=8·t∂, … etc to the maximum value ts≤100 s, (where t∂ is the discretisation time interval of the vector n(t)); calculating the parameter ηj using (1) for each value tsj, and for that value from tsj=tem for which the parameter assumes maximum value ηm; calculating the estimate value of the unknown distance between the detector and the ionising radiation source using the formula R*=kk·υ0·tem, where υ0 is the mean velocity of the detecting system, coefficient kk is equal to 2.0-2.8 depending on the design of the detector. EFFECT: high accuracy of estimating the location of a detected source.