The native arteriovenous fistula (nAVF) is the ideal access in patients in hemodialysis, however, traditionally requires a period of maturation from its surgical construction that usually takes more than 8 weeks, exposing patients to a longer time with catheters; In this article, we describe 4 cases of early cannulation (<3 weeks) based on nursing staff expertise and ultrasound criteria. Keywords: vascular access, arteriovenous fistula, maturation, cannulation, renal insufficiency, ultrasound.