Assessment of site fertility is usually based on measurements of the growth of the present stand or the composition of the field vegetation. In this study, the soil nutrient availability, assessed using in situ ion-exchange resin (IER) bags, was tested as a possible predictor of forest production. Ten Scots pine sites and five Norway spruce sites, distributed throughout Sweden, were included in the study. At the pine sites, the amounts of NO3 adsorbed by the IER correlated best to forest production ( pB 0.001), although the abundance of this ion was low. Only a weak correlation with production was found for K+ (pB 0.1). The IER adsorption of PO4 was low at the pine sites in southern Sweden.