Abstract Objective. The incidence of urogenital tumours is constantly increasing as a result of over-proportional ageing of the population in industrialized nations. Follow-up of non-muscle-invasive bladder cancer (NMIBC) primarily relies on the detection of either relapse or progression and does not include screening for second malignancies. This study investigated the incidence of independent non-urothelial second malignancies and associated risk factors in patients with NMIBC. Material and methods. The charts of 380 consecutive patients (297 men and 83 women) with newly diagnosed NMIBC over a 16-year period at a Swiss hospital were analysed retrospectively. Age, stage of bladder tumour, smoking status, and occurrence of second and third malignancies were registered. Observed incidences of independent non-urothelial malignancies were compared with age- and gender-specific rates based on data from the National Institute for Cancer Epidemiology and Registration by calculating standardized incidence ratios (SIRs). Results. Mean age at first NMIBC diagnosis was 69.9 years. Histological stage of the NMIBC was pTa in 241 patients (63.4%), pT1 in 102 (26.8%)and pTis in 37 (9.7%). During follow-up, 62 independent non-urothelial second or third malignancies were observed in 48 men (16.2%) and 10 women (12.0%). In male patients, prostate and lung cancer (SIR 4.3 and 5.7, respectively) were more frequent than expected in the general population, as were lung and uterine cancer in women. Conclusions. Follow-up in patients with NMIBC should pay special attention to independent non-urothelial malignancies. Investigations for non-urological malignant disease, especially for lung cancer, should form part of the standard follow-up in NMIBC patients.