Two hundred and one patients had biopsies of their native kidneys with ultrasound-guided needle technique. They were evaluated on the second post-biopsy day with colour-coded Doppler sonography. Ten patients out of these 201 were found to have an arteriovenous fistula, which remained asymptomatic for the whole follow-up period (follow-ups ranged from 2 to 31 months). Four of these 10 patients developed a perirenal haematoma as well and five macroscopic haematuria. Our study shows that the systematic use of colour-coded Doppler sonography after renal biopsy facilitates diagnosis of arteriovenous renal fistula.