The increased diagnosis of small renal masses (SRMs) poses the challenge of how best to manage patients with tumours that are not likely to progress and cause death during their lifetime. Concerns regarding overdiagnosis and overtreatment of patients with low-risk or indolent disease has led to the introduction of active surveillance as an alternative to immediate intervention in select candidates. However, differentiating between benign or low-grade lesions and high-grade aggressive phenotypes is difficult. Renal biopsy, radiographic assessment, and clinical nomograms have been used before surgery to evaluate the probability of whether an SRM will exhibit characteristics of an aggressive cancer. SRM growth trends have been studied over periods of observation but no characteristics have been found to correlate with aggressive growth kinetics. Stratification of patients with SRMs according to risk status is crucial when considering whether active surveillance might be an appropriate treatment option. Factors that should be taken into account include comorbidities, a history of malignancy, pre-existing chronic kidney disease, life expectancy and patient preference. Standardized active surveillance protocols are currently lacking, and clinical trials designed to randomize patients with SRMs to receive either active surveillance or immediate treatment are sorely needed to address the existing evidence gap.