OBJECTIVE • To evaluate the influence of radiographic tumour size and other preoperative variables on the pathological characteristics of the lesion to determine the distribution of pathological features and assess preoperative risk factors for potentially aggressive versus probably indolent renal lesions. METHODS • Retrospective review of records for 768 patients who underwent surgery for single, sporadic renal mass between 2000 and 2008 in a tertiary academic institution. • Demographic, radiographic and pathological variables were recorded and analysed with regression analyses for risk factors for potentially aggressive pathological features (malignant pathology, high Fuhrman grade, lymphovascular invasion and extracapsular extension). RESULTS • Malignancy was pathologically confirmed in 628 (81.8%) specimens. • Radiographic size was significantly associated with malignancy (versus benign pathology; OR = 1.13, P= 0.001), high Fuhrman grade (OR = 1.21, P < 0.0001), vascular invasion (OR = 1.19, P < 0.0001) and extracapsular extension (OR = 1.23, P < 0.0001). • Age, symptomatic presentation, solid appearance and radiographic size were independent predictors of potentially aggressive disease, whereas for male gender (OR = 1.43, P= 0.062) a trend toward statistical significance was noted. CONCLUSIONS • Age, male gender, radiographic size and appearance, as well as symptomatic presentation, are associated with an increased risk of malignant, potentially aggressive disease. • These factors should be considered when evaluating management options for a solitary enhancing renal mass.