Ultrasonography is becoming a more commonly used diagnostic tool in the investigation of prostatic disorders in dogs. The anatomical position of the prostate can vary considerably depending on its size and tissue characteristics and so a number of choices of acoustic windows and transducer format have been proposed for the investigative technique. The purpose of this presentation is to evaluate these variations for the different types of pathology encountered in canine prostatic disease. Both sector and linear format scanners were used to examine a series of 25 (n = 25) dogs with a range of transducers including mechanical sector, microconvex linear and a dedicated human endorectal probe. Frequencies ranged from 3.75 to 7.5 MHz. The series included prostatic cyst and abscess, paraprostatic cyst, benign hyperplasia and neoplasia. The ultrasonographic appearance of the various pathological changes of the prostate was classified and the preferred imaging was in cross-section at the widest point with the urethra located centrally. This could usually be obtained from a prepublic window but the endorectal probe was of use where the diseased prostate was retained intrapelvically. The 7.5 MHz proved the transducer of choice for all but the largest dogs being of a microconvex format. Ultrasonographic imaging of the canine prostate proved to be a reliable diagnostic tool in the further investigation of canine prostate disease.