Synthetic horizontal branches, constructed on the basis of Sweigart and Gross (1976) horizontal branch star models and of the recently revised theoretical instability strip (Stellingwerf, 1984) are presented for various chemical compositions appropriate for Population II systems, for various assumptions on the mass size of the helium core and for cluster age in the range of 12 - 15 billion years. Some selected data, related with the pulsational properties of RR Lyrae pulsators and with the horizontal branch morphology, are analysed and compared with observed horizontal branches.