We aimed to analyse the expression patterns of the most promising class I HDACs (HDAC-1, -2 and -3) in a representative cohort of primary bladder cancers and correlated these to clinico-pathological parameters including tumour stage, grade, multifocality, adjacent carcinoma in situ, growth pattern and finally clinical follow-up data. This evidence concerns the gene HDAC1 and in situ carcinoma.