Aggression research is moribund. Lack of research over the past two decades has left many issues. (1) Understanding varieties of agonistic behaviour in an ethological context: categories differing in behaviours, target sites and function include offence, defensive attack, and predation. Biological systems must be determined for each of these. (2) Insuring availability of ethologically valid laboratory models of agonistic behaviour and describing (possibly species-specific) standards for these. We shall present models and consider the problematic issue of biting. (3) Use of non-damaging behavioural markers that precede fights. These should be independently analysed, measured and verified as potential substitutes for biting attack. (4) Interaction between fear and offensive aggressive motivation systems must be understood in order to evaluate whether independent variable (e.g. pharmacological, genetic) effects involve a specific motivational system rather than reflecting changes in oppositional systems. (5) Knowledge of agonistic systems and their biological basis must be extended to humans, focusing on both normal aggression in each category, and the development of models of aggressive psychopathology. Placing aggression research in an ethological context and focusing on its biomedical relevance may help to counter forces suppressing this work.