We investigated a head-to-tail regioregularity of poly(3-alkylthiophenes) from 3-alkylthiophene by an oxidative coupling polymerization, which is the simplest and easiest way for the synthesis of polythiophenes. The polymerizations were conducted using ferric chloride (III) as an oxidant in chloroform. Investigating the polymerization conditions, a lower temperature and a lower concentration were effective for increasing the head-to-tail (HT) content. The best HT content of 88% was obtained when the temperature was -45 degrees C and the initial monomer concentration was 0.02 mol L-1. Washing the resulting polymer by n-hexane further increased the content to 91%. Thus, it was found that the high regioselectivity can be achieved by the simple polymerization and the simple operation such as washing. The polymerization mechanism causing the regularity is also discussed.