The frequent use of intra-lesional injection of bacterial immunostimulants is hampered by apparent rarity of susceptible tumours, absence of therapeutic effect on large tumours, lack of variety of experimental models, eventual traumatism which is feared in case of intra-lesional, and injection in visceral cancers. (1) Methylcholanthrene induced primitive tumours in mice are more frequently susceptible when the carcinogen induction dosage is low (0.01 mg). (2) Using transplantable rat tumours, one susceptible and one resistant to intra-tumoral BCG or Corynebacterium parvum therapy, we have shown that both are resistant to systemic administration of immunostimulants. For the susceptible tumour, subcutaneous peritumoral multiple injections have the same efficacy as intra-tumoral injection in curing small tumours and ipsilateral distant tumours, when the rats receive a double graft of the same tumour. Superficial multifocal intratumoral injections can cure more voluminous susceptible tumours. The association of peritumoral and intra-tumoral injections rendered susceptible the usually resistant tumours.