Weight and height were followed longitudinally from birth to adulthood in children with inflammatory bowel disease living in a defined area of Sweden, 1983 through 1987; 124 children out of a possible 128 were studied. During the year preceding diagnosis, height growth velocity was significantly reduced in both ulcerative colitis and Crohn's disease. At the time of diagnosis, weight-for-height was subnormal in both children with ulcerative colitis (p < 0.05) and those with Crohn's disease (p < 0.001), while height was reduced only in children with Crohn's disease (p < 0.05). Weight for height was normalized within one year in ulcerative colitis, after the initiation of medical therapy. In Crohn's disease, weight-for-height improved during the years following diagnosis but height remained subnormal. Children with ulcerative colitis reached puberty at the normal time and their final heights became normal. In children with Crohn's disease, puberty was delayed (p < 0.001) and final height was reduced (p < 0.01). The impact of inflammatory bowel disease on growth was substantial, but it was smaller in this study than in many other published studies. The possible reasons for this difference include use of population-based material and a relatively short interval between the first symptoms and the start of treatment. Our findings indicate that, although final height was significantly reduced in children with Crohn's disease, delayed puberty reduced the negative effects on permanent adult height, to a certain extent compensating for the period of poor growth earlier in life.