These data belong to and include all variables for the statistical analyses conducted in the Plos One paper entitled “No clear associations of adult BMI and diabetes mellitus with non-muscle invasive bladder cancer recurrence and progression” by Jelle Evers, Anne J. Grotenhuis, Katja K.H. Aben, Lambertus A.L.M. Kiemeney, Alina Vrieling from Radboud University Medical Center, Nijmegen, The Netherlands. The objective of this paper was to determine the associations of BMI and diabetes mellitus with risks of recurrence and progression among non-muscle invasive bladder cancer patients. Data from the Nijmegen Bladder Cancer Study (NBCS) were used, as described in more detail in the paper. In short, non-muscle-invasive bladder cancer (NMIBC) patients who are registered in the Netherlands Cancer Registry (NCR), held by the Netherlands Comprehensive Cancer Organisation, were selected and invited to participate in the NBCS in four batches. Only NMIBC patients under the age of 75 years and who were diagnosed between 1995 and 2010 in one of seven hospitals in the mid-eastern part of the Netherlands were invited. Also, a non-overlapping series of 280 NMIBC patients who were previously recruited for a separate study on gene-environment interactions was included. Of all invited patients, 59% responded and filled out a questionnaire on general characteristics, medical history, lifestyle, and family history of cancer. The median time between diagnosis and filling out the questionnaire was 2.8 years (interquartile range: 1.8 - 6.7 years). Data on the primary tumour, treatment, and clinical follow-up were retrieved from medical files. A total of 1433 NMIBC patients were included.