This study involved 80 subjects, 46 of them were environmentally exposed to lead whereas 34 of socioeconomically matched subjects were not. The study aimed at investigating the effect of exposure to lead on the immune system, particularly the effect on the balance between type 1 (T-helper 1) and type 2 (T-helper 2) immune responses. This was done by careful history taking; clinical examination and performing some laboratory investigations (total blood lead (B-Pb) level, complete blood picture, total IgE, serum interleukin-4 (IL-4) and Gamma interferon (IFN-γ)) on the study subjects and detecting lead levels in the environment of exposed subjects. There was a statistically significant difference between exposed group and control group as regards serum IL-4 level (with higher levels in exposed group than control group) and to serum IFN-γ level (with lower levels in exposed group than control group). Also, a statistically significant negative correlation was found between B-Pb level and serum IFN-γ (r= -0.284, p= 0.011). Although the correlation between B-Pb level and serum IL-4 was not statistically significant (r= 0.141, p= 0.212), the sample size may have played a role in that as IFN-γ/IL-4 ratio had a statistically significant negative correlation to B-Pb level (r= -0.284, p= 0.011).