Bisdimethylamino-tri- (BDT), -penta- (BDP), -hepta- (BDH), and nonamethines (BDN) on surfaces were investigated with regard to detect absorption bands caused by aggregation. The experiments prove that the aggregation tendency increases with prolonging the chain length. A new method preparing non-aggregated and aggregated layers of heptamethines on surfaces of glass was used. X-ray results and RHEED measurements were compared. We think that a "thin layer modification" is formed.