One subject of the invention is a process for dyeing keratin fibres, especially the hair, using i)at least one hydroxybenzaldehyde derivative, ii)at least one oxidizing agent, and iii) at least one alkalinizing agent in the presence of heat. Another subject of the invention is a cosmetic composition for dyeing keratin fibres comprising the ingredients i)to iii)as defined previously. Another subject of the invention is a multicompartment device comprising the ingredients i),ii)and iii). This dyeing process makes it possible to obtain better colorations that are chromatic, intense and long-lasting without the use of oxidation bases such as para-phenylenediamines and para-aminophenols.
