Cancer treatments often induce oral complications. In this study we investigate longitudinally the salivary gland function, the salivary caries-related microorganisms, and buffer capacity in bone marrow recipients. Stimulated saliva samples were taken midmorning. The salivary factors were studied in 42 patients from before transplant until 4 months after transplant. A dramatic reduction (66%) of salivary flow rate is noticed in all patients at 1 month after transplant, and only a partial recovery (42% reduction) is seen after 4 months. A clear shift toward a lower buffer capacity and a higher amount of cariogenic microorganisms is seen posttransplant. This shift is more pronounced when total body irradiation was included in the pretransplant conditioning therapy. These findings indicate that the studied parameters in transplant recipients can contribute to a higher caries risk and oral complications during the early posttransplant period.