Compressing together divided barium and poly(para-phenylene) results in the intercalation of the metal into the polymer. Electron energy loss spectroscopy (EELS) analysis indicates that an intercalation level of 0.24 barium ions per phenyl unit can be achieved and that the oxidation state of the intercalated barium is rather +2 (Ba2+). Both transmission. electron microscopy and electron spin resonance studies show that the distribution of the intercalant in the polymer is very inhomogeneous.