The circulation of the HPAI virus can be studied at farm level, but relevant data gathered at other points in the poultry production chain, such as markets or collection points, help create a clearer picture of the virus'circulation, since these points are often more accessible than the farms. There is also potential for the virus to become concentrated at these points. Observation of critical points along the chain should draw a good picture of the virus' circulation. Either this could be used as a comparison with farm survey data, or it could provide more efficient and rapid detection of HPAI in a given context and production sector. The objectives of the present study are to analyze and describe flows and practices from the top to the bottom of the poultry marketing chain in two Provinces of North Vietnam to evaluate a HACCP-like risk scoring methodology and to identify critical points for the detection of pathogen circulation along these marketing chains. The qualitative description of poultry production sectors was based on questionnaires compiled between May and August 2008 on 240 poultry semi-commercial production farms and 60 collective interviews of backyard producers and 60 traders in Ha Tay and Bac Giang Provinces. Possible observation points were identified. The HACCP-like approach with a risk scoring methodology, tested on two points from the layer production sector, was able to discriminate between these two points. Our result confirms that this method could be used to identify a few critical observation points with a higher risk of virus circulation in the chain, where the early detection of HPAI virus would be most effective.