The comparative study of the human tumour cell line HeLa and rat liver sections for the detection of antinuclear antibodies by the indirect immunofluorescence technique demonstrates the superiority of HeLa monolayer in sensitivity and specificity. Use of monolayers is essential for the diagnosis of antinucleolar and anticentromere ANA specificities and permits differentiation between anti-Sm/RNP, anti-SS-B and anti-Scl-70. ANA profiles are evaluated in 142 sera of 72 patients with different forms of lupus erythematosus and scleroderma and in 216 sera of healthy subjects.