<i>Background:</i> Sunflower seed oil (SSO) effect on solid and ascitic forms of Ehrlich tumor was evaluated. <i>Methods:</i> Solid or ascitic Ehrlich tumor-bearing Swiss mice were treated daily, by subcutaneous route, with 200 µl of SSO. The solid tumor-bearing footpad was measured every 3 days and ascitic tumor-bearing mice had their ascites collected and quantified. At the end of the SSO treatment, the total cell number in lymphoid organs was quantified. <i>Results:</i> Subcutaneous treatment with SSO inhibits the solid tumor growth and increases lymph node cell number in animals with solid tumor, but has no effect on animals with ascitic tumor. <i>Conclusions:</i> SSO can delay the solid tumor growth, possibly due to better absorption of this treatment by draining lymph nodes.