Fecal calprotectin is a marker of inflammatory and neoplastic disease in the lower gastrointestinal tract. A new fecal sample preparation procedure for the measurement of calprotectin has been developed, with higher calprotectin yield and lower contamination risk. Changes in the new method compared to the original [Roseth AG, Fagerhol MK, Aadland E, Schonsby H. Assessment of the neutrophil dominating protein calprotectin in feces. A methodologic study. Scand J Gastroenterol 1992;27(9):793-798] are smaller sample size, higher dilution of the sample, presence of dissociating agents in the extraction solution and procedure performed in closed disposable tubes. The extraction yield was 78% (41-100%) of total calprotectin, giving an overall five-fold increase compared to the original method. Samples with high calprotectin values were increased to a slightly higher degree, than low calprotectin samples, thus improving the separation between high and low calprotectin levels. Median calprotectin level in healthy subjects was 26 microg/g. Pathological samples with pancolitis showed levels up to 30000 microg/g. The mean C.V. (coefficient of variation) in blended feces was lower than that of unblended, suggesting uneven distribution of calprotectin. However, no significant difference between spot measurements was found when five samples from each of 47 stools were measured. Thus measurements of calprotectin in fecal samples were accurate and reproducible. No interference with foods or relevant oral pharmaceuticals or nutraceuticals was found.