Death of cells in the control. - (Dec/15/2010 )

Hi guys,
I am doing toxicity experiments,but I have a problem. I usually add my drug to the cells and icubate it for a certain time, then measure the absorbance and compare it with the control, which has no drug in it. But I can see that some of the cells of my control are dead as well, I can see some holes, which means some of the cells have come off. Do you know why this might be?

Thanks

You normally get some dead cells in any cell population - this is the reason you have controls... to show that the level of death (in your case) is greater with treatment than without.