The usefulness of the whole sample taking in filter paper for the detection of anti-HAV IgM is described. 168 serum and filter paper samples were simultaneously compared. No alterations were observed in the specificity of the enzyme-linked immunosorbent assay for the catchment of IgM in the 52 samples of the control group or in the other 116 from patients with clinical suspicion of acute viral hepatitis. A sensitivity, specificity and coincidence of 100% was obtained on comparing the filter paper with the dilution 1:500 with the serum. The correlation established between the values of optical density of the positive results to anti-HAV IgM, the filter paper at dilution 1:500 and the serum was of 0.895. On applying this type of sample taking in a group of hospitalized patients, 100% of coindicence with clinical suspicion was attained. Besides, it was proved its usefulness for the diagnosis of a viral hepatitis outbreak. According to our results, it is recommended the introduction of this type of sample taking in the diagnosis of hepatitis A.