Plant condition assessment using remote sensing techniques have been associated with spectral vegetation indices such as the normalized difference vegetation index （NDVI）. A change in NDVI values has been normally regarded as changes in vegetation amount or density. The spectral properties of plants

which are directly related to the health conditions

would also result in changes in spectral vegetation indices. Consequently

a lower vegetation index value may result from either lower density or nutrient stress

or a combination of the two. This would limit the use of vegetation indices as a monitoring tool. Bidirectional reflectance distribution function （BRDF） models treat plant density and optical properties differently and

therefore

can help to assess plant condition objectively. In this study

multiangular spectral reflectances were measured over two winter wheat canopies: one being under nitrogen stress and the other not. These multiangular measurements were then used in inversions of BRDF models to estimate the optical properties and the plant densities. The results show that it is feasible to obtain simultaneously the optical properties and plant densities and

therefore

it is possible to use BRDF models and multiangular remote sensing measurements to make diagnostic analysis of nitrogen-related plant conditions. The results also revealed some limitations of this approach such as inversion problems and computation time.