2,5-Bis(4-propyl-2-pyrrolyl) thiophene was reacted with aryl aldehydes to afford large porphyrinoids; [24]dithiaamethyrin(1.0.0.1.0.0) and [36]trithianonaphyrin(1.0.0.1.0.0.1.0.0). X-ray crystallography of the dithiaamethyrin revealed a highly planar ring structure with mean plane deviation (MPD) value of 0.053 angstrom. A large positive NICS(0) value (+13.9 ppm) calculated for this planar 24 pi system unambiguously indicates an antiaromatic character that is consistent with a remarkably low field H-1 chemical shift of the inner NH proton at 24.0 ppm. The magnitude of the paratropic ring current effect in the 24 pi amethyrin framework in the free base form and the diprotonated form was discussed on the basis of the MPD value and the NICS value. The present dithiaamethyrin is much more strongly antiaromatic than the dodecaalkylamethyrin in their free base forms, but the order inversed in their di-protonated forms.