The Fourth International Workshop on Plant Mitochondria continues a series of informal and interactive gatherings for researchers in the fields of plant mitochondrial genetics, biochemistry, physiology and molecular biology. This Workshop is the only forum for a large number of researchers in the field to interact. The format requires that all attendees present either a poster and/or a short talk, thus maximizing their degree of participation. The specific objectives of the Workshop are to provide an informal atmosphere for the exchange of ideas and current data, to facilitate and encourage the establishment and continuation of existing scientific collaborations, and to hold concurrent workshops on specialized topics and thus to identify critical research objectives in the understanding of mitochondrial function and biogenesis. The Workshop will be at Cornell University, where there is active research in plant organelle molecular biology, biochemistry and transformation. Several significant advances have occurred since the last Workshop, including the discovery of RNA editing in plant mitochondria, mitochondrial transformation and the complete sequence analysis of a plant mitochondrial genome. The upcoming Workshop promises to be the most scientifically stimulating to date, and has already attracted widespread interest including inquiries or accepted invitations from nearly 100 scientists from 15 countries.