Bakteriozni rak masline je bolest uzrokovana bakterijom Pseudomonas savastanoi pv. savastanoi (Pss). Pss je vrsta koja pripada kompleksu vrsta Pseudomonas syringae. Mehanizam zaraze s Pss uključuje sintezu dvaju hormona rasta – auksina i citokinina, koji uzrokuju pojavu hipertrofiranog tkiva, odnosno nekontrolirane i ubrzane diobe stanica na različitim biljnim organima masline (Olea europaea L.). Prisutnost bakterioznog raka masline zabilježena je u gotovo svim maslinarskim regijama u svijetu. Tijekom dvije godine (2021. i 2022.) obavljeno je terensko istraživanje i uzorkovanje zaraženog biljnog materijala kako bi se utvrdila prisutnost ovog patogena i na području hrvatskog dijela istarskog poluotoka. Ukupno 102 uzorka sakupljena su s 22 različite sorte u 45 maslinika. Prisutnost patogena određena je molekularnom metodom Real - time PCR u 32 (30 %) uzorka. Najveći udio pozitivnih uzoraka činile su sorte Leccino i Frantoio, koje su ujedno bile najzastupljenije sorte u istraživanim maslinicima. Veći tumori na simptomatičnim stablima masline utvrđeni su u sjevernim dijelovima Istre. Olive knot disease is caused by bacterium Pseudomonas savastanoi pv. savastanoi (Pss). The bacterium Pss belongs to the Pseudomonas syringae species complex. The mechanism of action used by Pss to establish an infection involves synthesis of two types of growth hormones - auxins and cytokinins. This mechanism leads to uncontrolled and accelerated cell division in different plant organs of olive tree (Olea europaea L.), which cause the appearance of hypertrophic tissue, known as knots. The presence of bacterial olive knot disease is recorded in almost all olive-growing regions in the world. In this research, a field survey and sampling of symtomatic plant material was carried out during 2021 and 2022 with aims to determine the distribution of olive knot disease in the Croatian part of the Istrian peninsula. Totally 102 samples were collected from 22 various olive varieties in 45 orchards. The bacterium Pss was identified using the Real-time PCR method in 32 (30%) of tested samples. The highest number of positive samples was recorded from susceptible Leccino and Frantoio varieties, which were the most widely grown varieties in sampled orchards in Istria. The formation of larger tumours on symptomatic olive trees was observed in olive orchards located in more northern regions of surveyed area.