Abstract: The results of the dynamics among the percentages of granulomas vs. eggs' mean diameters in lung tissues in four groups of mice suggested that: 1. Low dosages of SEA 0.01-0. 1μg/g, q.d. × 14 by hypodermic injection may induce certain levels of low dose (or zone) tolerance in unsensitized mice; 2.There was a tendency of high dose tolerance, although it was not induced with the dosage used (2.5μg/g) by hypodermic injection; 3. Granuloma reactions in groups with low dosages of SEA were significantly higher at 24 hr after egg injection, but they became significantly lower from day 5 on. The reaction peak in the control group was on day 16 after egg injection, while in groups with low dosages of SEA was on day 10.Observations on the population dynamics of various types of cells of Schistosoma ja-ponicum egg granulomas showed that: 1. Lymphocytes, macrophages and fibroblasts often slightly increased within the first 3 days and lowered down between day 10 and day 16 after egg injection; 2. Eosinophils were higher at the first day and began to decline on day 4 and remained at a level lower than that in control group; 3. Populations of Neutrophils, plasma cells, giant cells and collagenous fibers were all roughly similar and in small numbers,