Positive Systems are dynamic systems in which the relevant variables assume nonnegative values. These systems are quite common in applications where variables represent positive quantities such as populations, consumption of goods, densities of chemical species, probabilities etc. The development of theoretical models which take into account this positivity requirement has been a very active field of research for a long time. This volume contains the contributions for The Second Multidisciplinary Symposium on Positive Systems:Theory and Applications (POSTA06) held in Grenoble, France, August 30-31 and September 1, 2006. Theses contributions cover several theoretical issues (stability, control properties, ...) concerning the models of positive systems as well as many application papers in the fields of biology, communication systems, etc.