In CERES-rice, at ISTAGE = 1, it is calculated the daily growth of leaf area per plant: MPLAG = A / CUMPH * (-BF) * XTN * EXP(XTN) * TI * TSHOCK * AMIN1(TURFAC, TEMF, AGEFAC). I donīt know the meaning of some of these factors and cannot find them at the world related bibliography. Could somebody help me to solve this problem?. What is A?, a constant = 3800?, CUMPH is the number of fully expanded leaves?. Is BF previous day leaf weight? (BF=0,12). XTN=-9,678*EXP(-BF+CUMPH). XTN?. TI=DTT/(PHINT*PC), TI=leaf fraction emerging in one day?. PHINT=83šC.day.leaf-1, phyllochron. PC=0,66+0,068*CUMPH. Where at the literature could I get the meaning of variables that compose CERES-rice?. During three rice crop cycles I collected field information to validate CERES-rice and to adequate it to our conditions must know how it was built. As an example I cannot match the measured grains per panicle with the simulated values, how can I find a solution if I donīt know the meaning of some variables that determine it?. Sincerely yours: Luis E. Alvarez L. Universidad Ezequiel Zamora. UNELLEZ. Guanare. Estado Portuguesa. Venezuela