The variability of interstellar atomic lines, sporadically reported in the astronomical literature, has been confirmed both in the case of the nearby hot star delta Ori and the very young and violent star-forming region eta Carinae, using high-resolution echelle spectra. The presented variability concerns the intensities and profiles of Na I, KI and Ca II. The time-scale of the above-mentioned variations clearly suggests very local phenomena as their cause. It is important to say that not all interstellar lines vary in unison.