Laying hens were fed with feed from the Belgian dioxin incident diluted ten-fold with non-contaminated feed, resulting in concentrations of 61ngTEQkg −1 PCDD/Fs, 23ngTEQkg −1 non-ortho PCBs, 116ngTEQkg −1 mono-ortho PCBs and 3.2mgkg −1 of the seven indicator PCBs. Following exposure for seven days, feed was replaced by non-contaminated feed for a period up to six weeks.Concentrations of PCDD/Fs in eggs showed a maximum of 214pgTEQg −1 fat after nine days and decreased to 44pgTEQg −1 after seven weeks. Dioxin concentrations in abdominal fat of chickens killed just after the last treatment, or after 1, 3 or 6 weeks on clean feed were 69, 84, 54 and 41pgTEQg −1 fat, respectively. Concentrations in livers decreased more rapidly, being 35, 7, 4 and 3pgTEQg −1 tissue, respectively. In both eggs and tissues, total TEQ concentrations were 3–4 times higher.Concentrations of the seven indicator PCBs in egg fat showed a stronger decrease with concentrations of 16.5μgg −1 at the peak (day 9) and 2.2μgg −1 after seven weeks. Corresponding concentrations in abdominal fat were, respectively, 4.6 and 2.6μgg −1 fat, and in livers 0.77 and 0.14μgg −1 tissue.The ratio of indicator PCBs to PCDD/Fs in feed was 52200. In eggs this ratio was initially higher (85000), but decreased towards 50000 after six weeks on clean feed. In abdominal fat the ratio varied between 49000 and 67000. In livers, the ratio was initially low (22000) but increased to 45000 towards the end of the study. It is concluded that the behaviour of PCDD/Fs and PCBs in laying hens is comparable and that the use of indicator PCBs appears to be a good alternative for PCDD/Fs but only in the case of co-exposure to both PCBs and PCDD/Fs, such as in incidents with PCB oil.