Perhaps, the comparison of the new fluorescent dyes Cy3, Cy5 (and maybe others?) with their more established counterparts in the use with secondary antibodies has been a topic of discussion on this list before. If this is the case could someone please direct me to the archive, if it is not I would like to find out: 1) how much stronger (unbleachable) are they? 2) how stable are the conjugates during storage? 3) how do they perform as double labels? 4) what are the disadvantages of the new dyes (I have heard of background problems)? 5) why are the old fogies still around (is there a significant price difference)? Christoph Viebahn Institute of Anatomy University of Bonn Germany