A randomised clinical trial in primary care with a 12-months follow-up period. About 135 patients with acute sciatica (recruited from May 2003 to November 2004) were randomised in two groups: (1) the intervention group received physical therapy (PT) added to the general practitioners' care, and (2) the control group with general practitioners' care only. To assess the effectiveness of PT additional to general practitioners' care compared to general practitioners' care alone, in patients with acute sciatica. There is a lack of knowledge concerning the effectiveness of PT in patients with sciatica. The primary outcome was patients' global perceived effect (GPE). Secondary outcomes were severity of leg and back pain, severity of disability, general health and absence from work. The outcomes were measured at 3, 6, 12 and 52 weeks after randomisation. At 3 months follow-up, 70% of the intervention group and 62% of the control group reported improvement (RR 1.1; 95% CI 0.9-1.5). At 12 months follow-up, 79% of the intervention group and 56% of the control group reported improvement (RR 1.4; 95% CI 1.1; 1.8). No significant differences regarding leg pain, functional status, fear of movement and health status were found at short-term or long-term follow-up. At 12 months follow-up, evidence was found that PT added to general practitioners' care is only more effective regarding GPE, and not more cost-effective in the treatment of patients with acute sciatica than general practitioners' care alone. There are indications that PT is especially effective regarding GPE in patients reporting severe disability at presentation.