Considering the importance of addressing issues commonly encountered in daily medical practice, the authors, as part of the continuing medical education of family doctors, have decided to publish a series of articles in the field of urology. These articles briefly present the current state of knowledge on the most frequently encountered urological conditions for which patients typically first consult a family doctor. The first topic in this series is simple renal cysts in adults, excluding multilocular cysts, polycystic kidney disease, medullary cystic disease, multicystic dysplasia, and hydatid cysts. Renal cysts are typically a round structure, most often located on the surface of the kidney, less frequently originating from the medulla. It is filled with clear fluid, has a thin wall lined with a single layer of cuboidal or flat epithelium – sometimes atrophic – and usually lacks septations or calcifications, and are discovered incidentally during ultrasound examinations performed for other indications, provided the cyst is > 1 cm in diameter. In about 70% of cases, the cysts are solitary and unilateral, predominantly located in the lower pole of the kidney. Currently, ultrasound (US), computed tomography (CT), and magnetic resonance imaging (MRI) are the standard imaging tools.