Antinuclear antibodies (ANA) provide a powerful tool in diagnosing the connective tissue diseases. The fundamentals of antinuclear antibody testing and the sensitivity, specificity, and prognostic value of antinuclear antibodies and their associated illnesses will be discussed. As skin manifestations are common with connective tissue diseases, knowledge of the diagnostic and prognostic value of ANA testing is essential to the nurse in dermatology.