Nodes from 45 men treated for syphilis in varying stages of the disease were studied. Five of these nodes contain treponeme-like forms which were virulent in 2 cases. A node study after supervised treatment was negative in all 5 men. Possible reinfection and inadequacy of previous treatment are probably important factors in the original findings. Penicillin is the drug of choice in the treatment of syphilis. There is no evidence that Treponema pallidum survives in humans after adequate penicillin treatment.