1. A progress report of clinical observations in the therapeutic use of tridione on 136 cases of varied neurological manifestations, over a period of 2 years, is presented.2. As previously reported, most spectacular benefits were obtained in cases of petit mal, where clinical improvement was immediate, associated with improvement in [SEE TABLE2 IN SOURCE PDF] the EEG pattern, and sustained often after cessation of the drug.3. Tridione appears to be useful as an adjuvant drug in the treatment of grand mal seizures, though it does seem to aggravate some cases.4. Both grand and petit mal of the idiopathic type were more responsive than those due to organic lesions.5. Anticonvulsant action is indicated by its beneficial effects in cases of tetanus.6. Tridione is of value in cerebral palsy, especially for reducing tension of the athetoid type.7. Some forms of behavior disturbances are sedated by tridione.8. Site of action for tridione appears to be the midbrain and (with some selectivity) the basal nuclei, an inference drawn from its failure to help patients with pyramidal lesions, while markedly benefiting extra-pyramidal lesions, with the exception of chorea, parkinsonism, and dystonia.9. Toxic side-effects in the use of tridione, in our experience, were rare in children, were generally innocuous, and seemed readily reversible with cessation of the drug. More severe reactions were seen in adults.