Contents: Preface. J.M. Flach, The Ecology of Human-Machine Systems: A Personal History. P.A. Hancock, M.H. Chignell, On Human Factors. K.J. Vicente, A Few Implications of an Ecological Approach to Human Factors. A. Kirlik, Requirements for Psychological Models to Support Design: Toward Ecological Task Analysis. J. Rasmussen, A.M. Pejtersen, Virtual Ecology of Work. D.D. Woods, Toward a Theoretical Base for Representation Design in the Computer Medium: Ecological Perception and Aiding Human Cognition. J.M. Flach, R. Warren, Active Psychophysics: The Relation Between Mind and What Matters. W.H. Warren, Jr., Constructing an Econiche. B.S. Zaff, Designing with Affordances in Mind. M.J. Dainoff, L.S. Mark, Use of a Means-End Abstraction Hierarchy to Conceptualize the Ergonomic Design of Workplaces. R.E. Shaw, O.M. Flascher, E.E. Kadar, Dimensionless Invariants for Intentional Systems: Measuring the Fit of Vehicular Activities to Environmental Layout. G.P. Bingham, M.M. Muchisky, "Center of Mass Perception": Affordances as Dispositions by Dynamics.