Technetium-99m hexamethylpropylene amine oxime labelled leucocyte scintigraphy (LS) was performed on 45 occasions in 30 patients with ulcerative colitis and on 53 occasions in 34 patients with Crohn's disease. Serial images were taken following re-injection of the labelled leucocytes. The segmental extent of the inflammation and the grade of the leucocyte uptake were calculated, and compared with the laboratory results and colonoscopy findings. The sensitivity and specificity of LS proved higher in ulcerative colitis (87% and 93%) than in Crohn's disease (53% and 89% in cases with large intestine involvement, and 82% and 100% in cases with small intestine involvement). The activity of the process determined by LS correlates with the alpha 2-globulin level (r = 0.47), fibrinogen level (r = 0.50), fS iron level (r = -0.57), sedimentation (r = 0.44), leucocyte count (r = 0.38), platelet count (r = 0.34) and Best index (r = 0.31) in ulcerative colitis, but not in Crohn's disease.