The objective of the present study was to determine whether indomethacin, an inhibitor of prostaglandin synthesis, could improve shell quality in birds laying a high incidence (greater than 15%) of soft-shelled (SS) and shell-less (SL) eggs and in birds laying exclusively hard-shelled (HS) eggs. Treatments consisted of two injection types, indomethacin or oil (controls), and two injection times, 4 h or 16 h postentrance of the egg into the uterus. Indomethacin delayed oviposition in both HS and SS or SL egg layers, with indomethacin being more effective in delaying oviposition when injected at 16 h as compared with 4 h postentrance of an egg into the uterus. Indomethacin increased shell thickness of the first egg laid following injection in the SS or SL groups but not in the HS groups. Egg weight was not affected by indomethacin injection. It was concluded that indomethacin delayed oviposition and prevented the premature expulsion of some SS or SL eggs. This delay in oviposition resulted in thicker shells of the first egg laid postinjection.