BACKGROUND: The prognostic value of the clinical findings elicited in the patient presenting with sciatica is unknown. AIM: To investigate whether history and physical examination findings can predict outcome. DESIGN OF STUDY: Prospective study of prognostic factors. SETTING: A sample of primary care patients with sciatica. METHOD: Short-term favourable outcome was registered as improvement perceived by the patient after two weeks. Long-term failure was defined as eventual surgery or lack of improvement after three months. RESULTS: The signs and symptoms that most consistently predicted an unfavourable outcome were: a disease duration of more than 30 days; increased pain on sitting; and more pain on coughing, sneezing or straining. The straight leg raising test and, to a lesser degree the reversed straight leg raising test, were the most consistent examination findings associated with poor outcome. Chances of short-term improvement were also related to the body weight relative to the length. CONCLUSION: The predictors in this study can indicate the prognosis of patients with sciatica at an early stage. Knowledge of these prognostic factors may help to fine tune treatment decisions and improve patient selection in trials of conservative therapy strategies.