Abstract : Lead-containing pigments (red lead, white lead), widely employed in paintings since Antiquity, are liable to undergo transformations which lead to discolorations of the pictorial layer (blackening, whitening, greening). The conditions of appearing of the alteration phases are studied through artificial ageing tests of raw pigments and experimental paintings. The tests reveal both the decomposition of white lead in the presence of lime and the transformation of minium into black plattnerite b-PbO2 in dilute acidic environment. The characterization of red lead micro-samples taken from an experimental wall painting after a 25-years natural ageing period reveal that blackening is linked to the formation of plattnerite through a probable mechanism of disproportionnation of Pb3O4 in acidic environment. The whitening is cause by the re-crystallization of divalent lead into both cerusite (PbCO3) and anglesite (PbSO4), produced by the absorption of gaseous pollutants (CO2, SO2).