The clonogenic assay is a microbiology technique for studying the effectiveness of specific agents on the proliferation of cells. (The term "clonogenic" refers to the fact that these assays use colonies of cells that are clones of one another.) Clonogenic assays are frequently employed in cancer research laboratories to determine the effect, if any, of a drug, radiation, or a combination of both on proliferating tumor cells. After applying the drug and/or radiation, one measures the percentage of cells that survive the treatment.

Traditionally, the cell colonies are counted by hand under a microscope, which makes the process exceedingly tedious. Automated counters do exist, though; in addition, one can sometimes use a commercial yeast or bacterial colony counter to automatically enumerate the colonies in question.

Also see: Immunogenic