To investigate the histological effect of intranodal injection of the streptococcal preparation OK-432, we performed intranodal injection in 4 patients with cervical lymph node (CLN) metastases of malignant head and neck tumors (squamous cell carcinoma (SCC) of the oropharynx, SCC of the parotid gland, malignant lymphoma, and rhabdomyosarcoma of the nasal cavity). An initial dose of 5 klinische Einheit (KE) and a maintenance dose of 10 KE of OK-432 were administered into each metastatic or residually involved CLN twice a week. The total dose of OK-432 ranged from 105 KE to 395 KE and the number of administrations ranged from 11 to 40. Post treatment histological examination of excised tissue specimens revealed no tumor cells; there was only fibrosis and inflammatory cell infiltration. These findings suggest that intranodal injection of OK-432 can be utilized for treatment of relatively small CLN metastases of malignant head and neck tumors.