Several epidemiological studies have suggested a possible seasonality in the presentation and course of inflammatory bowel disease. Our aim was to investigate whether in our area there is a seasonality in the presentation and evolution of inflammatory bowel disease. In this retrospective evaluation 255 patients were included, of whom 141 patients were diagnosed with ulcerative colitis and 114 with Crohn's disease according to conventional criteria, with histological confirmation in 225 patients. Relapse was defined as the development of symptoms that required an increase or change in the usual treatment. Periods of activity were related to the month and grouped within one of four seasonal periods: December to February, March to May, June to August and September to November. Bouts of ulcerative colitis and Crohn's disease were most frequently diagnosed in the period June to August (p < 0.05). Both diseases showed similar seasonality, and analysis of the 305 attacks did not show any significant trend. In conclusion, inflammatory bowel disease begins more frequently in the period June to August, but its course does not show consistent seasonal variations.