On the basis of high‐resolution spectrometry and NLTE analysis we investigate abundance patterns of non‐nuclear origin in normal main‐sequence A stars and in their metal‐deficient counterparts, the Lambda Bootis stars. We try to identify and separate the effects of diffusion (gravitational settling, radiative levitation) and accretion (separation of gas and dust) on the surface composition. Two blue stragglers in the old open cluster M67 are compared with the normal A stars in an attempt to trace the signature of anomalous stellar evolution.