Objective: This study investigates the clinical and demographic characteristics of familial Mediterranean fever (FMF) patients with and without amyloidosis. Patients and methods: The clinical data of 503 patients with FMF (females: males 250: 253) were reviewed. Fifty of these patients had amyloidosis (f:m 23: 27). Results: The ages of attack onset in patients with and without amyloidosis were 7.8 +/- 6.2 and 11.1 +/- 8.5, respectively (P < 0.05). The time between disease onset and diagnosis was longer in patients with amyloidosis than those without (187.6 +/- 99.4 months and 132.5 +/- 110.2 months, respectively, P < 0.001). More patients in the amyloidosis group had positive family histories of FMF (68% vs 54%, P < 0.05). The frequencies of chest pain (78% vs 51%, P < 0.001), arthritis (80% vs 60%, P < 0.01), and erysipelas-like erythema (44% vs 16%, P < 0.001) were higher in the amyloidosis group. Conclusion: In the amyloidosis group, FMF-related manifestations of chest pain, arthritis, and erysipelas-like erythema are more frequent. Our results also support that long periods between disease onset and diagnosis are associated with a high risk of developing amyloidosis.