Open-air preaching or "street preaching" is the practice of preaching to people in public places. While this may provoke images of ragged-looking men with sandwich-boards reading "The End is Nigh!", it is currently gaining popularity among certain evangelical Christian ministries. Ray Comfort's Way of the Master series, for example, includes videotaped footage of this tactic and his Living Waters ministry (along with several others) offers instructional courses covering open-air evangelism.
This tactic isn't limited to street corners or public grounds: shopping centers, college campuses and conventions are considered prime targets. While mass preaching is often practiced, another popular tactic is to focus on one-on-one conversations with individuals.