La93 is a program for computing the precession and obliquity of the Earth for various values of 1) the tidal effect of the Moon (CMAR) 2) the dynamical ellipticity of the Earth (FGAM) The nominal solution La90 corresponds to (CMAR = 0., FGAM = 1). The general solution will be called La93(CMAR,FGAM), thus La90 = La93(0.,1.) and La93(1.,1.) is obtained with the same tidal effect as in Quinn, Tremaine, Duncan (1991), although these solutions are not completely identical (see Laskar, Joutel, Boudin, 1993) The files and software of this package can be used in three different manners: 1) Contruction and Use of the nominal solution La93(0,1) The ASCII files ORBEL*.ASC contain the nominal orbital solution. The ASCII files PREC0*.ASC contain the nominal precession solution. The ASCII files CLIVAR0*.ASC contain the nominal climatic solution. The files PREC*.ASC and CLIVAR*.ASC can also be generated from the enclosed files (see section 2) For the computation of insolation quantities, the user will execute the 'prepinsol' step, and then 'insola'. 2) Construction of a parametrized La93(CMAR, FGAM) new solution The user reconstructs a complete La93(CMAR, FGAM) solution. The compilation of all required programs is obtained by running the command 'make' on a Unix machine. The preparation step 'prepa' needs to be done once, in order to prepare the necessary binary files. Then 'integ' will construct the new solutions for the given parameters (CMAR, FGAM). Alternatively, change in the Makefile the values of CMAR and FGAM before running the 'make clean' command (removes the files computed using the preceding values of CMAR and FGAM), and 'make La93'. 3) Changes in the model of precession, for example to take into account some feedback resulting from redistribution of the ice on the Earth resulting from climate changes. In this case, and in this case only, the user needs to edit the FORTRAN file integ.f More precisely, the subroutines which can be eventually modified are SUBROUTINE INIPRE(IPT) SUBROUTINE PRECES(t,AK,AH,AQ,AP,DK,DH,DQ,DP,AKI,DKI) The users may also want to adapt the driver INTEG to his specific needs