For patients from 18 out of 33 study centers the period between qualifying event and treatment is known: this cohort consists of 338 patients treated with CAS according to the SPACE-protocol (63% of the entire CAS-per protocol cohort) and 325 patients treated with CEA (58%). 104 (30.8%) CAS- and 117 (36.0%) CEA-patients were treated within 14 days after the index event (p0.16; Fishers exact test). Baseline data did not differ significantly between the groups. In patients treated early with CAS the endpoint ‘ipsilateral stroke or death occurred in 9.6%, in those treated later in 5.1% (Odds-ratio (OR) 1.95; 95% confidence interval (95%CI) 0.80 to 4.77). In patients treated early with CEA the endpoint occurred in 3.4%, in those treated later in 3.8% (OR 0.88; 95%CI 0.23 to 2.99). The OR for the comparison of early treated CAS with CEA-patients is 3.00 (95%CI 0.93-11.3; p0.06) in favor of surgery, for later treatment the OR is 1.35 (95%CI 0.54-3.53; p0.53). Conclusion: In contrast to CEA the periprocedural risk of the CAS-cohort seems to be dependent from the timing of intervention; having a higher risk with early treatment. Hence, for patients with symptomatic carotid artery stenosis which can be treated early, CEA seems to be the safer method. This might be due to increasing plaque stabilization over time and therefore a reduced risk for later endovascular therapy.