In order to study water use by fruit crops, 9 experimental campaigns were performed in France and Portugal between 1988 and 1997 in commercial orchards (apple, plum, peach) and vineyards. In this paper, some of the data collected were used to assess the use of various fruit crop characteristics for estimating the maximal transpiration (MT) of plants from the reference evapotranspiration (ETo). In the following experiments, transpiration was measured on 5 to 8 representative plants by built-in sap flow gauges. The climatic conditions above the plots were measured: incident and reflected solar radiation, net radiation, air temperature and humidity, wind speed and direction. The reference evapotranspiration ETo was estimated using the Penman equation. The geometry of the rows was represented using simple shapes, and the porosity of the rows was estimated in most experiments. The amount of solar radiation absorbed by rows was measured in some orchards, and was estimated by a simple geometrical model for vineyards. Then the fraction of net radiation absorbed by the rows was evaluated. The leaf area of the plants was also determined in most cases. MT was deduced from mean plant transpiration in well irrigated or in wet soil conditions for vineyards. For fully developed foliage, MT/ETo varied between 0.2 and 1.0. The results were compared to the fractional ground cover, the ground fraction shaded by a row, the amounts of solar and net radiation absorbed by the foliage, and the leaf area index LAI. Except for the vineyard, with tall and narrow rows, MT/ETo can be well estimated by the fraction of ground shaded by a row or the ground cover fraction. By considering the amount of solar radiation or net radiation absorbed by a row, the estimation of MT/ETo is improved for vineyard and the orchard-vineyard ensemble, but not for orchards. The best estimation is obtained from the leaf area index, but this data is very difficult to obtain.