Daily and seasonal gas exchange of fourteen rainfed almond tree varieties, grafted in six-year old GF677, was monitored in the field. Pre-dawn leaf water potential changed from May to October which shows a reduction in soil water availability despite some precipitation in October. As a consequence, net photosynthesis (Pn) and stomatal conductance (Gs) decreased for most varieties, although it did not in 'José Dias' and 'Duro d'Estrada'. Decreases in Pn and Gs were observed from morning to afternoon in both periods. Pn maintained reasonably high values after harvest in all varieties probably due to increases or maintenance of pressure potential in some varieties. Although low, the precipitation in the first days of autumn and the increases in soluble sugars and-or proline could have contributed to maintain plant water status and photosynthetic activity. Increases of WUEi were observed in 'Duro d' Estrada', 'Duro Italiano', 'José Dias' and 'Verdeal'. Overall, the Portuguese variety 'José Dias' showed the best photosynthetic performance.