The direct macrophage and indirect leukocyte migration inhibition tests were used for the examination of patients with pulmonary tuberculosis and of their contacts. In the direct test at a concentration of 10 microgram PPD/ml medium, a statistically significant difference [p less than or equal to 0.001] was found between the mean values of MI [migration indices] in PPD-negative [MI = 0.98 +/- 0.10] and MI of PPD-positive to patients [MI = 0.60 +/- 0.10]. [PPD-negative = showing no reaction to ID administration of tuberculin, PPD-positive = showing a positive reaction to ID administration of tuberculin]. A statistically significant difference [p less than or equal to 0.05] was also found between the mean values of MI in tuberculin-positive to patients and healthy contacts [MI = 0.80 +/- 0.14]. By means of the indirect test we demonstrated a statistically significant inhibition of migration [p less than or equal to 0.001] in PPD highly positive contacts [MI = 0.76 +/- 0.10]. The results of the direct and indirect migration inhibition tests were found to agree in 66.6%.