Gartner Inc, a world’s leading research and advisory company has developed a methodology how to identify leading companies in a particular market segment. The so called Magic Quadrant uses two complex criteria, “completeness of vison” and “ability to execute” to group possible vendors into four groups: leaders, visionaries, challengers and niche players. Based on the Gartner reports the paper shows who are the leading companies in the data mining industry for the last five years. The corresponding data mining systems are briefly introduced as well.