I have seen alot of woman asking if PLAN B WORKS ON OVULATION. and most the answers are wrong. Well to relax any individuals whom are im a worry for that. Plan b is a emergancy pill to prevent pregnancy, it can be taken at any time of the months cycle. Second- if it didnt work during or after ovulation the plan b offical website would tell you also your pharmasist would advise you although non explain therefore this pill works when needed. Third- take plan b within 12-24 hour window for a 99% effectivness. Within the 72 hour window is fine aswell and is 90% effective. I hope i helped with stress!.