Public campaigns to increase stroke preparedness have been tested in different contexts, showing contradictory results. We evaluated the effectiveness of a stroke campaign, designed specifically for the Italian population in reducing prehospital delay. According to an SW-RCT (Stepped-Wedge Cluster Randomized Controlled Trial) design, the campaign was launched in 4 provinces in the northern part of the region Emilia Romagna at 3-month intervals in randomized sequence. The units of analysis were the patients admitted to hospital, with stroke and transient ischemic attack, over a time period of 15 months, beginning 3 months before the intervention was launched in the first province to allow for baseline data collection. The proportion of early arrivals (within 2 hours of symptom onset) was the primary outcome. Thrombolysis rate and some behavioral end points were the secondary outcomes. Data were analyzed using a fixed-effect model, adjusting for cluster and time trends. We enrolled 1622 patients, 912 exposed and 710 nonexposed to the campaign. The proportion of early access was nonsignificantly lower in exposed patients (354 [38.8%] versus 315 [44.4%]; adjusted odds ratio, 0.81; 95% confidence interval, 0.60-1.08; P=0.15). As for secondary end points, an increase was found for stroke recognition, which approximated but did not reach statistical significance (P=0.07). Our campaign was not effective in reducing prehospital delay. Even if some limitations of the intervention, mainly in terms of duration, are taken into account, our study demonstrates that new communication strategies should be tested before large-scale implementation. URL: http://www.clinicaltrials.gov. Unique identifier: NCT01881152.