External factors have the potential to act as immunostimulants in order to influence the body's protection from many foreign antigens. We intended to investigate the ethanol extract Formulary of F-MaCg effect as an immunostimulant.A purely experimental with a completely randomized design was used on twenty-four white male rats. They were divided into four groups:1) G0 [given aquades (5 ml)]; 2) G1 [given F-MaCg-75 mg/gr BW (Body Weight)]; 3) G2 (F-MaCg -150 mg/gr plus Hepatitis B vaccine at the beginning and the end of treatment); and 4) G3 (F-MaCg -300 mg/gr BW plus hepatitis B vaccine at the end of treatment). The rat's spleen lymphocyte blast transformation was evaluated on the 15th and 37th days. Lymphocytes were examined using microtetrazolium assays. Optical Density (OD) was measured using an ELISA reader [493 nμ (nanomicro)]. Observation of lymphocyte viability by a counting chamber using a light microscope and trypan blue 1% before being cultured with Phytohaemoaglutinin.Lymphocyte cell viability in the hepatitis B vaccine-induced group on the 15th day showed the highest average value in the G2 (1,484/mcl of blood); on the 37th day, it was in G3 (1,578/mcl of blood). The proliferative activity of spleen lymphocytes indicated by the difference in the OD values of the four treatment groups was 0.467, 0.913, 1.619, and 1.473 nμ, respectively. Histological observations of the spleen showed differences at all given formulary dose concentrations.F-MaCg could be an immunostimulant because of its ability to trigger a cellular immune response.