Polythiophene films have been deposited on a platinum electrode surface by direct oxidation of thiophene in BF3-ethyl ether solution containing a controlled amount of water (5 mM). The electric and mechanical properties of the films were studied. Experimental results demonstrated that the films prepared at low applied potentials were semiconductors with conductivities in the order of 10(-1) s cm(-1). The strengths of these films were high and comparable to those of some widely used engineering plastics such as poly(propylene) and poly(vinyl acetate). The conductivities of the PT films varied with the value of applied potential used for electrolysis and passed through a maximum of 19.13 s cm(-1) at 1.6 V. At a given applied potential, low experimental temperature; and monomer concentration led to formation of films with high quality.