A new gas-phase technology for polyolefin production is being developed to be commercially available for large-scale production between 2004 and 2005. This new technology uses a multilane circulating reactor, which consists of two interrelated zones where two distinct and different fluodynamic regimes are realized, between which the polymer particles are kept in continuous circulation. This article presents a mathematical model for the multilane circulating reactor presenting the typical behavior of the reactor operation and a parameter sensibility analysis. Simulations were conducted for polyethylene production. (C) 2004 Wiley Periodicals, Inc.