Before one asks, “Are mass evangelistic events effective?” one must ask, “Are massevangelistic events Biblical?” Careful study reveals it is Biblical to preach to large crowds of people. In the Old Testament, Jonah was commanded by God to preach to the evil city of Nineveh. At first, Jonah did not want to go, but after a roundabout journey, he finally made it to Nineveh. In response to his preaching, the entire city repented, including the king.
Jesus frequently preached to large crowds of people (Matthew 4:25; 5:1; 7:28; 8:1; 15:30; 19:2; 22:23; 23:1). When Jesus saw the crowds, he had compassion on them (Matthew 9:36). Such “large crowds” came to hear Jesus that he was forced to retreat to a boat in order to preach (Matthew 13:2). On one occasion, Jesus preached to a crowd of 5,000 men plus woman and children (Matthew 14:21). With a wife and a child for each man, this yields a number of at least 15,000 people.
Peter preached to a large crowd on the day of Pentecost and three thousand people were saved in response to a single sermon (Acts 2:41). Philip, the only person specifically called an evangelist in the Bible, preached to “crowds” in Samaria (Acts 8:6). Many people were healed and baptized because of his ministry. In Pisidian Antioch, the entire city gathered to hear Paul and Barnabus preach the Gospel (Acts 13:44). Later they preached to a large number of Jews and Gentiles in Iconium (Acts 14:1) and Lystra (Acts 14:18). Paul and Silas preached to “large numbers” of God-fearing Greeks in Thessalonica (Acts 17:4). In Athens, they preached in the synagogues and in the marketplace (Acts 17:17) and in front of the Areopagus (Acts 17:22).
Theologically, the necessity for evangelism is obvious. The church is always one generation away from dying out. The growth of the church is dependent upon new people being saved on a regular basis.