Background The presence of a few renal cysts is considered of little relevance in healthy adults, although acquired renal cystic disease occurs in advanced kidney failure. The objective of this study was to detail renal cystic and solid lesions and identify any association with clinical characteristics. Study Design Clinical-pathologic correlation. Setting & Participants Potential kidney donors undergoing a standardized evaluation at the Mayo Clinic in 2000-2008. Predictors Age, kidney function, and chronic kidney disease risk factors. Measurements Renal cystic and solid lesions by contrast-enhanced computed tomographic images. Outcomes Cyst number, diameter, and location. Results After excluding 8 with cystic disease, 7 of whom had autosomal dominant polycystic kidney disease, there were 1,948 potential kidney donors (42% men; mean age, 43 years). A cortical, medullary, or parapelvic cyst ≥5 mm was present in 12%, 14%, or 2.8%. For ages 19-49 years, 39%, 22%, 7.9%, and 1.6% had a cortical or medullary cyst ≥2, ≥5, ≥10, and ≥20 mm in diameter. For ages 50-75 years, 63%, 43%, 22%, and 7.8% had a cortical or medullary cyst ≥2, ≥5, ≥10, and ≥20 mm in diameter. The 97.5th percentile for number of cortical and medullary cysts ≥5 mm increased with age (10 for men and 4 for women in the 60- to 69-year group). After age and sex adjustment, cortical and medullary cysts ≥5 mm were associated with higher 24-hour urine albumin excretion, as well as increased body surface area, hypertension, and higher glomerular filtration rate in some analyses. Angiomyolipomas, hyperdense cysts, and enhancing masses or cysts with concerning features for malignancy occurred in 2.2%, 1.2%, and 0.6% and were associated with older age ( P ≤ 0.05 for each). Limitations Persons with known chronic kidney disease were excluded. Conclusions Renal cysts are common, particularly in older men, and may be a marker of early kidney injury because they associate with albuminuria, hypertension, and hyperfiltration.