The monolayer stability of polyamic acid salts (PAAS) increases as the chain length of salts increases and the hysteresis of the π-A isotherms is found when compressed and expanded. The transferabilities of the monolayers were sharply influenced by the stability at the interface, but not affected by the dipping conditions. In a well-balanced condition, the Langmuir film is transferred as a Y-type on various substrates. The thickness of PAAS was found to be 16.7 Å. After imidization, it was reduced to 5.6 Å per layer, but some ordered structures sustained.