We wish to extend a warm welcome to the readers of the First International Workshop on Knowledge and Data Mining Grid (KDMG’05) proceedings. This workshop was held in June 2005, in conjunction with the 3rd Atlantic Web Intelligence Conference 2005 (AWIC’05). In the last decade, Grid computing has become one of the most important topics to appear and one of the most widely developed fields. Research into Grid computing is making rapid progress, owing to the increasing necessity of computation resources in the resolution of complex applications. Knowledge is playing an important role in current grid applications, allowing researchers to investigate aspects related to services discovery, service composition and service brokering. KDMG’05 aimed to provide a forum for novel topics related to Knowledge and Data Mining Grid, providing an opportunity for researchers to discuss and identify key aspects of this important area. The set of technical papers presented in this volume comprises the KDMG’05 selected papers. We can say that this selection was the result of a difficult and thorough review process. The KDMG’05 workshop received 22 submissions of high quality from which the 8 papers making up the technical program were selected. The number of submissions and the quality and diversity of the resulting program are testimony to the interest in this up-and-coming area.