Thermal conversion of poly(anthranilic acid) (PANA) to polyaniline (PAn) has been studied by means of thermogravimetric/mass (TG/MS) and Fourier transform infrared (FTIR) spectroscopy. The electrical conductivity of the chemically prepared PANA was 3.5 x 10(-2) S/cm, which is caused by the self-doping of the polaronic nitrogen atom interacting with the ionized carboxyl group (-COO-). The heat-treated PANA can be assumed to be identical to an emeraldine base of PAn. The pyrolysis of PANA. proceeded through the decarboxylation at two stages from carboxyl (-COOH) and ionized carboxyl groups, which occurred at about 170 and 230 degrees C, respectively. PANA-SA, which was prepared by treating PANA at 250 degrees C and then doping with an external protonic acid at room temperature, showed a considerably high conductivity (6.2 S/cm). The composite consisting of PANA-SA and poly(vinyl alcohol) was very sensitive to the environmental humidity. The logarithm of electrical conductivity of this composite was proportional to the relative humidity covering more than five orders of magnitude, and the change in conductivity extended from 4.2 x 10(-5) to 10 S/cm upon the humidity variation from 14 to 91%.