Photospheric carbon, nitrogen, and oxygen abundances of A-type main-sequence stars *

Based on the spectrum fitting method applied to CI 5380, NI 7486, and OI 6156-8 lines, we determined the abundances of C, N, and O for 100 mostly A-type main-sequence stars (late B through early F at 11000K>Teff>7000K) comprising normal stars as well as non-magnetic chemically peculiar (CP) stars in the projected rotational velocity range of 0km/s N>O. Regarding the considerable star-to-star dispersion observed at any Teff, the most important cause is presumably the difference in rotational velocity. These observational facts appear to be more or less favorably compared with the recent theoretical calculations based on the model of atomic diffusion and envelope mixing.