We report here the first evidence for planetesimal infall onto the very young Herbig Be star LkH _ { \alpha } 234 .
These results are based on observations acquired over 31 days using spectroscopy of the sodium D lines , the He I 5876Å , and hydrogen H _ { \alpha } lines .
We find Redshifted Absorption Components ( RAC ) with velocities up to 200 km/s and very mild Blueshifted Absorption Components ( BEC ) up to 100 km/s in the Na I lines .
No correlation is observed between the appearance of the Na I RAC & BEC and the H _ { \alpha } 
and He I line variability , which suggests that these ( Na I RAC & BEC ) are formed in a process unrelated to the circumstellar gas accretion .
We interpret the Na I RAC as evidence for an infalling evaporating body , greater than 100 km in diameter , which is able to survive at distances between 2.0 to 0.1 AU from the star .
The dramatic appearance of the sodium RAC and mild BEC is readily explained by the dynamics of this infalling body making LkH _ { \alpha } 234 the youngest ( age \sim 0.1 Myr ) system with evidence for the presence of planetesimals .