The ability of dipropylacetic acid (DPA) and dipropylacetamide (DPM) to modify EEG and seizure activity was assessed in 4 female and 3 male Papio papio. Doses of 30-60 mg/kg of DPA given at intervals over an 8 h period produced blood levels of 19-44 micrograms/ml which were not protective against intermittent light stimulation (ILS). Administration of 150-200 mg/kg doses at intervals over a 36 h period produced blood levels greater than 150 micrograms/ml and were highly protective against ILS. Similar results were obtained following adminstration of DPM; however, DPM appeared to offer greater protection against ILS. A moderate amount of seizure control was obtained at blood levels of 60-91 micrograms/ml (DPA) and complete blockade occurred at levels greater than 100 micrograms/ml DPA. Background EEG changes were similar following either DPA or DPM and consisted of a striking increase in total spectral power with relative power changes in 10-20 c/sec range, the magnitude of which was related to blood levels of DPA. Both agents produced a quieting effect on behavior without severe depression.