Serum interleukin-6 (IL-6) was measured in picograms/ml (pg/ml) using an immunoassay (ELISA) in healthy individuals (n = 148), of whom 128 were classified as dextral and 20 as non-dextral, as per a laterality questionnaire. Only 3 (15%) non-dextral individuals had serum IL-6 levels above the lower limit of the assay sensitivity as compared to 59 (46%) of dextral individuals (P < 0.013). There were no significant correlations between previously determined mitogen stimulated interleukin-2 production and autoantibodies in a subset of the same individuals. While this data does not provide casual information, it adds to the evidence of the asymmetric regulation of immune functions by the cerebral hemispheres.