Several prognostic factors have been recognized in patients with multiple myeloma (MM). Among the most important are: the serum levels of beta2-microglobulin, albumin, and LDH; the labeling index; and an abnormal karyotype. Patients with amyloidosis (AL) have poor prognosis; however, little is known concerning the prognostic significance of AL associated to MM. In 201 consecutive patients with de novo MM, we performed a fat-pad biopsy needle aspiration (FPBNA) that was stained with Congo red. Sixty eight (34%) patients had AL and a poorer prognosis disease: lower performance status, presence of B symptoms, higher LDH and calcium values, and worse response to chemotherapy. Cox regression model for overall survival detected three variables having independent prognostic significance: the presence of AL (RR = 3.4, P < 0.004), serum albumin levels <3.5 g/dl (RR 3.2, p < 0.005), and patients not achieving complete remission or very good partial remission (RR 2.9, p < 0.02). In 28% of patients with de novo MM, FPBNA was useful to detect incidental amyloidosis. During follow-up, 69% of these patients had symptoms of AL. Excluding 16 patients with obvious symptoms of AL at diagnosis, overall survival was worse in patients who developed later symptoms of AL. MM-associated AL represents a poorer prognosis disease even in the absence of symptoms at diagnosis, and this specific association may be considered as an independent high-risk prognostic factor. The routine study of periumbilical fat-pad tissue should be mandatory in all patients with MM.