Following a request from the European Commission, the Panel on Additives and Products or Substances used in Animal Feed (FEEDAP) was asked to deliver a scientific opinion on the safety and efficacy of annatto F (alkali-processed norbixin, acid-precipitated) for cats and dogs. Norbixin is considered safe for cats at a maximum concentration of 13 mg/kg complete feed and for dogs at 16 mg/kg complete feed. Annatto 2.5% is a strong alkaline solution of potassium or sodium hydroxide that makes it corrosive and therefore harmful for the user. Although the ability of the additive to colour feed has generally been demonstrated, no conclusion on the effective concentration can be drawn.