This volume is devoted to modern accomplishments in the field of vector lattices and integral operators which were achieved in Russia during the last two decades. Nonstandard methods are elaborated for the analysis of vector lattices and positive operators. Much attention is paid to studying stability under multiplication by an arbitrary bounded operator for various classes of operators which are defined in terms of order. Also, several approaches to the solution of the J. von Neumann problem on the conditions for integrability of a linear operator are treated, and full information is given on the solution of some problems posed by P. Halmos and V. Sunder. Audience: This book is intended for mathematicians, students and postgraduates interested in functional analysis, operator theory, geometry of Banach spaces and vector lattices.