The standard (p-degrees = 0.1 MPa) molar enthalpies of formation of some crystalline aminosulfonic acids were determined at the temperature 298.15 K by rotating-bomb calorimetry. DELTA(f)H(m)degrees (cr)/(kJ.mol-1) NH2CH2SO3H (aminomethanesulfonic acid) -727.3+/-1.1 NH2CH2CH2SO3H (2-aminoethanesulfonic acid) -774.5+/-0.9 o-NH2C6H4SO3H (2-aminobenzenesulfonic acid) -599.6+/-1.1 m-NH2C6H4SO3H (3-aminobenzenesulfonic acid) -606.2+/-1.8 p-NH2C6H4SO3H (4-aminobenzenesulfonic acid) -612.3+/-1.0 The difference between DELTA(f)H(m)degrees (cr) for an NH2RSO3H and the corresponding NH2RCO2H has been found to be constant : -(198+/-2) kJ.mol-1.