Fifty randomly selected asthmatic patients were studied. In each the sex, age, time of onset of symptomatology, symptomatologic score (from 0 to 3), blood eosinophilia, IgE by the PRIST method and Tart cells in blood (investigated by the same method as is used in the search of LE cells in collagen diseases) were considered. Tart cells were recognized as in Miale Haemotology (9) as monocytes and occasionally polymophonuclar leucocytes with one or two round inclusions in their protoplasm owing to the phagocytosis of leukocyte nuclei. In contrast with LE cells, these inclusions are not homogeneous contain chromatin and nuclear membrane material and often have a dark ring of hyperchromic material. We have found that these cells can not be evoked passively by application of patient serum to normal leukocytes. In no case of positive Tart cells was antinuclear serum factor found by immunofluorescence as seen in lupus erythematous disease. 33 per cent of the 50 asthmatic patients tested had Tart cells in their blood. They were very scarce, only one or two in four Wright stained smears. This fact is probably why these cells were not recognized before. The positive Tart cell group was on the average the same age as the negative group. On the other hand, in the positive Tart cell group the proportion of men with respect to women, the time span from the onset of asthmatic symptoms (p less than 0,05), the symptomatology score (p less than 0,005) and blood eosinophilia (p less than 0,005) were increased. In contrast IgE was decreased on the average (p less than 0,05).(ABSTRACT TRUNCATED AT 250 WORDS)