Hi Stephen, Im not quite sure what sort of data you need, but if you only require relative values as you described then isnt it enough just to see the levels going up and down. In my experience this could be all you could realistically expect with immunofluorescence. Observations I have from biochemistry and morphology would suggest that two times the fluorescence does not mean two times the amount of antigen, even if the detection system were perfectly linear. I would wonder whether any attempt to get more absolutely quantitative answers would be just like adding an extra decimal place to an answer which was already wrong! Just my own feelings on the subject. Matthew Dr. Matthew Hannah Institute for Neurobiology, Im Neuenheimer feld 364 D-69120 Heidelberg, Germany WWW: http://129.206.50.220/Neurobiology.html Tel: ++49 (6221) 54-8320 or 54-8692 Fax: ++49 (6221) 54-8301