MH134 (5 x 10(5) in 0.1 ml of normal saline) was inoculated subcutaneously into the hind foot pad of C3H/He mice. The mice were divided into three groups on day 11 after inoculation. Each mouse in the first group (n = 12) received an intra-lymph nodal injection of 5KE of OK-432 in 0.1 ml of normal saline (OK-432 ILN group). The second group (n = 12) underwent subcutaneous injection of OK-432 (of the same dose) into the back (OK-432 SC group). The last group received no OK-432 (untreated group). Three hours after treatment the left popliteal lymph node was excised and the left hind foot at the knee joint was removed in each mouse. The mice were then observed for 90 days after treatment. Mice that died underwent autopsy and the left popliteal, inguinal, lumbar and suprarenal lymph nodes were excised for weighing. The survival rates were 10/12 for the OK-432 ILN group, 2/12 for the OK-432 SC group and 2/12 for the untreated group. The differences between the survival rate of the OK-432 ILN group and those of the other two groups were statistically significant (p less than 0.001). The lymph nodes were heavier in the OK-432 SC group and the untreated group than in the OK-432 ILN group. We concluded that intra-lymph nodal injection of OK-432 is very effective for treating lymph node metastasis.