We used moderately high-resolution, high S/N spectra to study the chemical composition of 10 field ab-type RR Lyrae stars. A new temperature scale was determined from literature Infrared Flux Method measures of subdwarfs and the Kurucz (1992) model atmospheres, and used to calibrate colors for both dwarfs and RR Lyraes. The applicability of Kurucz (1992) model atmospheres in the analysis of RR Lyraes at minimum light was analyzed: we found that they are able to reproduce colors, excitation and ionization equilibria as well as the wings of Halpha. We derived abundances for 21 species. The metal abundances of the program stars span the range -2.50

59 pages, Latex using aaspp.sty, ps-files of text, tables (21) and figures (23) available from ftp://boas3.bo.astro.it/pub/gisella To appear in October 1995 Astronomical Journal