A new model of the isolated perfused lung from different strains of mice was developed. Lungs from Swiss, Balb/C and CBA mice actively sensitised to ovalbumin were challenged intratracheally (i.t.) by antigen on day 14. In Swiss mice instillation of ovalbumin led to the release of leukotriene (LT) C4 significantly above basal values. Conversely, lungs from Balb/C and CBA mice were unresponsive to ovalbumin in terms of production of LTC4. All strains failed to release histamine when challenged with antigen. Intratracheal instillation of platelet-activating factor (PAF), to lungs from non-sensitised animals, induced the release of comparable amounts of LTC4, irrespective of the strain. In contrast, i.t. administration of fMLP to lungs from Swiss mice elicited release of significantly higher amounts of LTC4 as compared to Balb/C and CBA mice. In separate experiments, ovalbumin was injected into the paws and anaphylactic oedema was evaluated. Balb/C and CBA required 1 microgram to show an oedema formation, whereas the dose of ovalbumin for Swiss mice to develop a similar response was at least 30-fold lower. In conclusion, antigen provocation induced release of LTC4 from lungs from Swiss mice but not from Balb/C or CBA. This difference may be accounted for by strain-dependent factors, such as antibody production and requires further investigation.