Accurate LTE abundances of seven well established lambda Bootis stars

High resolution and high signal-to-noise CCD spec tra were analyzed to dete rmine accurate LTE abundances for seven well established lambda Bootis star s (a group of A to F-type stars with strong underabundances of Fe-peak elem ents whereas the C, N, O and S appear to be solar abundant): HD 31295, HD 1 25162, HD 142994, HD 149303, HD 192640, HD 204041 and HD 221756. In general , 13 elements were investigated. The effective temperatures of our program stars range from 7200 to 9000 K. The main results are the following: C, O, Na and S seem to be nearly solar abundant for all investigated stars. A wide range of underabundances within the individual stars exists for all other elements. No correlation of the individual abundances with astrophysical parameters s uch as T-eff, log g and v sin i was found. These results are consistent with the accretion/diffusion model which is cu rrently adopted for the explanation of the lambda Bootis phenomenon.