1. Contrary to N-methyl substituted formylpyrazoles 3(5)-formyl-5(3)-methylpyrazole (VII) and 3(5)formylpyrazole (VIII) are high melting compounds (5,6,7) which are less soluble in water and in the most common organic solvents than N-methylsubstituted formylpyrazoles. In our hands IR spectra taken in potassium bromide discs or in Nujol mull did not show a strong absorption band which can be assigned to a C=O stretching vibration. A preliminary mass spectral investigation indicated the presence of dimera. Spectra obtained with a MS 902 instrument (ionizing voltage 70 eV, temperature 60°) contained peaks of twice the molecular weights: Calcd. for 3(5)-formylpyrazole: mol. wt., 96.0324(C4H4N2O) mol. wt., dimer, 192.0647(C8H8N4O2). Found. C, 96.0318 and 192.0646. Calcd. for 3(5)-formyl-5(3)-methylpyrazole: mol. wt., 110.0482(C5H6N2O) mol. wt., dimer, 220.0960 (C10H12N4O2). Found: 110.0484 and 220.0957.