AIM: The Western diet typically consists of high levels of saturated fat from animal products and has been associated with an increased risk of bladder cancer. Whilst olive oil, the predominant fat in the Mediterranean diet, has been associated with many health benefits its role in bladder cancer aetiology is still unknown. Therefore, we investigated the effect of intake of animal products, olive oil and other major dietary fats on bladder cancer risk. METHODS: Dietary data were collected from 200 cases and 386 controls participating in a Belgian case-control study on bladder cancer. We calculated odds ratios (ORs) and 95% confidence intervals (CIs) by comparing the highest with the lowest tertiles of intake between cases and controls using unconditional logistic regression. Adjustment was made for age, sex, smoking characteristics, occupational exposures and calorie intake. RESULTS: There was a statistically significant inverse association between olive oil intake and bladder cancer consistent with a linear dose-response relationship: middle versus the lowest tertile (OR: 0.62; 95% CI: 0.39-0.99) and the highest versus the lowest tertile (OR: 0.47; 95% CI: 0.28-0.78; p-trend=0.002). We also observed borderline statistically significant increased odds of bladder cancer for the highest versus the lowest intake of cheese (OR: 1.53; 95% CI: 0.95-2.46; p-trend=0.08). No potential associations were detected for any other source or type of dietary fat. CONCLUSION: We observed evidence for a protective effect by olive oil and a possible increased risk of bladder cancer associated with a high intake of cheese. Our results require further investigation and confirmation by other studies.