Five novel azo calix[4]arenes were reported. The p-aminobenzaldehyde was diazotized with sodium nitrite in aqueous hydrochloride solution. Mono-, bis-, tris- and tetrakis(p-formylphenyl)azo calix[4]arenes (including proximal and distal isomers) were obtained respectively by diazo-coupling in different molar ratio to calix[4]arene (1) under pH=7.5-8.5 at 0-5 degreesC. All (p-formylphenyl)azo calix[4]arenes were characterized by H-1 NMR, C-13 NMR, IR, MS (ESIMS) spectroscopies and elemental analysis.