  We derived atmospheric parameters and spectroscopic abundances for C and O
for a large sample of stars located in the Hertzsprung gap in the
Hertzsprung-Russell Diagram in order to detect chemical peculiarities and get a
comprehensive overview of the population of stars in this evolutionary state.
We have observed and analyzed high resolution spectra (R = 60 000) of 188 stars
in the mass range 2 - 5 Msun with the 2.7 m Harlan J. Smith Telescope at the
McDonald Observatory including 28 stars previously identified as Am/Ap stars.
We find that the C and O abundances of the majority of stars in the Hertzsprung
gap are in accordance with abundances derived for local lower mass dwarfs but
detect expected peculiarities for the Am/Ap stars. The C and O abundances of
stars with Teff < 6500 K are slightly lower than for the hotter objects but the
C/O ratio is constant in the analyzed temperature domain. No indication of an
alteration of the C and O abundances of the stars by mixing during the
evolution across the Hertzsprung gap could be found before the homogenization
of their atmospheres by the first dredge-up.
