Antiphospholipid antibodies are the key and specific laboratory tests to help diagnosing antiphospholipid syndrome. Misinterpretation of these antibodies may result in misdiagnosis and more important inappropriate management. Transient positivity of these antibodies during acute illnesses, interference from other conditions, assay variability and other factors such as anticoagulant use are only some of the challenges for the clinicians. For an accurate diagnosis, testing should be carried out in stable clinical contexts, confirmation must be done on two occasions at least 12 weeks apart (unless there is a clinical thrombotic event—in the absence of other known causes—then according to the new criteria, moderate to high titres of aPLs appear to be sufficient for diagnosis) and more importantly, clinical data, other laboratory tests and past medical history of the patient should always be available. Patients with positive isolated antiphospholipid antibodies may lead the clinician in wrong treatment decisions, as not all positive individuals develop antiphospholipid syndrome. In addition, overlapping autoimmune conditions, such as systemic lupus erythematosus, may complicate the interpretation of results. By using standardised assays, knowing about patient’s current medication, testing for other relevant autoantibodies and listening carefully to the patients’ symptoms, an accurate diagnosis can be achieved.