We evaluated performance of the TEST 1 (SIRE Analytical Systems, Udine, Italy), a fully automated analyzer for the measurement of the erythrocyte sedimentation rate (ESR). Intra-assay reproducibility was satisfactory for a wide range of ESR values, whereas there was a significant decrease in ESR data when the samples were stored at 4 degrees C for up to 24 hours. We compared TEST 1 with the Westergren ESR method approved by the International Council for Standardization in Haematology (ICSH) and with the Diesse Ves-Matic analyzer Linear regression analysis comparing the TEST 1 and the ICSH reference method yielded satisfactory correlations for K3 EDTA- and sodium citrate-anticoagulated samples. Bland-Altman analysis showed no evidence of a systematic bias between the TEST 1 and the reference method. A close correlation was found between the TEST 1 system and the Diesse Ves-Matic analyzer despite a significant positive systematic bias. Reference values for men and women were analyzed according to nonparametric statistics. The TEST 1 was easy to use, had a satisfactory operative practicability required minimal maintenance, and reduced contact with potential biohazards. This system enables the determination of ESR with any common standard-sized tube; the use of samples anticoagulated with K3 EDTA can widely reduce the workload in clinical laboratories.