Plenary Talks -- Reputation Systems and Nonnegativity -- Lyapunov Exponents and Uniform Weak Normally Repelling Invariant Sets -- Reachability Analysis for Different Classes of Positive Systems -- Invited Sessions -- On the Positive LQ-Problem for Linear Discrete Time Systems -- The Importance of Being Positive: Admissible Dynamics for Positive Systems -- Detectability, Observability, and Asymptotic Reconstructability of Positive Systems -- Stability Radii of Interconnected Positive Systems with Uncertain Couplings -- Linear Operators Preserving the Set of Positive (Nonnegative) Polynomials -- Convergence to Consensus by General Averaging -- Stability and D-stability for Switched Positive Systems -- On Positivity and Stability of Linear Volterra-Stieltjes Differential Systems -- Eigenvalue Localization for Totally Positive Matrices -- Positivity Preserving Model Reduction -- The Minimum Energy Problem for Positive Discrete-Time Linear Systems with Fixed Final State -- A Rollout Algorithm for Multichain Markov Decision Processes with Average Cost -- Analysis of Degenerate Chemical Reaction Networks -- k-Switching Reachability Sets of Continuous-Time Positive Switched Systems -- Contributed Papers -- Inverse-Positive Matrices with Checkerboard Pattern -- Some Remarks on Links between Positive Invariance, Monotonicity, Strong Lumpability and Coherency in Max-Plus Algebra -- Stability Analysis and Synthesis for Linear Positive Systems with Time-Varying Delays -- Linear Programming Approach for 2-D Stabilization and Positivity -- An Algorithmic Approach to Orders of Magnitude in a Biochemical System -- Structural Identifiability of Linear Singular Dynamic Systems -- On Positivity of Discrete-Time Singular Systems and the Realization Problem -- Multi-Point Iterative Methods for Systems of Nonlinear Equations -- Identifiability of Nonaccessible Nonlinear Systems -- Trajectory Tracking Control of a Timed Event Graph with Specifications Defined by a P-time Event Graph -- Tropical Scaling of Polynomial Matrices -- Scrutinizing Changes in the Water Demand Behavior -- Characterization of Matrices with Nonnegative Group-Projector -- Robust Design of Water Supply Systems through Evolutionary Optimization -- Applications of Linear Co-positive Lyapunov Functions for Switched Linear Positive Systems -- A Problem in Positive Systems Stability Arising in Topology Control -- Control of Uncertain (min,+)-Linear Systems -- On a Class of Stochastic Models of Cell Biology: Periodicity and Controllability -- Implementation of 2D Strongly Autonomous Behaviors by Full and Partial Interconnections -- Ordering of Matrices for Iterative Aggregation - Disaggregation Methods -- The Positive Servomechanism Problem under LQcR Control.

This volume contains the proceedings of the "Third Multidisciplinary Symposium on Positive Systems: Theory and Applications (POSTA09)" held in Valencia, Spain, September 2–4, 2009. At present, this is the only world congress whose main topic is focused on this field. After this third event, the basis of a regular triennial event supported in the task of the previous organizing committees has become established.