Perilla frutescens is a Chinese herbal medicine. In this study, we prepared an extract of Perilla frutescens (PFE) and examined its effects on anti-DNP antibody responses in mice. The mice were immunized with DNP-ovalbumin in Alum adjuvant. To examine the effects of PFE on primary antibody responses, PFE was intraperitoneally injected the day before primary immunization. Anti-DNP IgE antibody production was found to be markedly suppressed by PFE injection. Then, we examined the effects on secondary antibody responses. PFE was injected only the day before secondary immunization. Anti-DNP IgE production was markedly suppressed, but IgG response was not so affected. These results suggest that the immunosuppressive effects of PFE are preferentially on IgE production and that PFE may be useful for the suppression of IgE antibody in certain allergic disorders.