The influence of the nuclear medium on the production of charged hadrons in semi-inclusive DIS has been studied by the HERMES experiment at DESY with a 27.5 GeV positron beam. The hadron multiplicity has been measured for helium, neon and krypton relative to that of deuterium. The multiplicity ratio is strongly reduced at high values of the atomic number A. The A-dependence of HERMES data on krypton and nitrogen is discussed and is compared to two theoretical models. Assuming a simple A^\alpha -dependence of the nuclear attenuation, the HERMES data are found to be closer to the A^2/3-dependence predicted by some pQCD-based models than to the A^1/3-dependence that follows from models based on nuclear absorption only.

PACS numbers: 13.60.Le, 13.60.Wb