Dear Rcurrie, Thanks for your reply. We do have a flow, but in another section of the lab. I use the trypan blue stain. I don't know the 7-aminoactinomycin D stain. the flow section get their own survey which includes what we get , so its also repetitive for them. Of the survey we only perform what our section does and thats the viability. Would using the second stain be an alternative, do you have a ref I could refer to for the procedure? What about the flow, what did you have in mind? Thank you again Liz