Little is known about referrals from primary care providers (PCPs) for suspected hematologic malignancies, including their clinical triggers and frequency. A random sample of 190 Massachusetts PCPs were presented with a vignette concerning a patient with a new finding of moderate anemia, asked how they would respond, and then asked what they would do if the patient returned with persistent anemia plus one additional sign or symptom. We also asked about referral behaviors for suspected hematologic malignancies during the prior year. A total of 134 (70.5%) PCPs responded. At first anemia presentation,only 3.8% reported referring to hematology. The development of a second sign or symptom yielded higher referral rates: pancytopenia 588.7%, leukopenia 5 63.9%, thrombocytopenia 5 63.9%, lymphadenopathy 5 42.9%, leukocytosis 5 37.6%, night sweats 5 25.6%, and weight loss 5 23.3%. The median yearly number (interquartile range) of patients PCPs reported suspecting of having hematologic malignancy was 5 (3, 10), and the median formally referred was 5 (3, 10). We conclude that anemia plus signs and symptoms suggestive of myelodysplasia or leukemia (compared with those suggestive of lymphoma) are more likely to prompt hematology referral. In addition, given their rarity,the numbe