Abstract Acetylsalicylic acid (aspirin) is an inhibitor of prostaglandin synthesis. Many soft-shelled (SS) and shell-less (SL) eggs are laid prematurely. It is hypothesized that prostaglandins may be responsible for the premature expulsion of some SS or SL eggs. The objective of the present study was to determine whether aspirin would reduce the incidence of SS or SL eggs and result in a concomitant increase in hard-shelled (HS) eggs. Layer breeders in their 15th mo of production were divided into groups of high and low incidence SS or SL egg laying and fed either control or rations with .05% aspirin for 4 wk. A decrease (P