Abstract： Objective To explore the diagnostic value of thyroid microcarcinoma with a taller-thanwide shape (A/T ≥ 1) in transverse ultrasonographic planes.Methods There were a total of 683 thyroid nodules in 491 patients undergoing consecutive ultrasonography and surgery at our hospital between 2011 and 2012.The ultrasonography examinations of thyroid nodules were routinely performed in the transverse planes.A taller-than-wide shape was defined as a ratio of anteroposterior diameter to transverse diameter in transverse plane ≥ 1.The sensitivity and specificity for thyroid carcinoma were analyzed.The data of thyroid carcinoma were formulated as follows:group 1,nodules ＞ 1 centimeter; group 2,≤ 1 centimeter.Their ratios of A/T were compared.The data were analyzed with SPSS 17.0 statistical software package.Results Among 683 nodules,499 were malignant and 184 benign.The sensitivity and specificity for malignancy were 61.5％ and 84.2％ respectively.There was significant difference (P =0.000).A taller-than-wide shape (A/T≥1) was more frequent in criterion 2 than criterion 1 (x2 =4.380,P =0.036).Conclusions A taller-than-wide shape (A/T≥ 1) is associated with thyroid malignancy especially thyroid microcarcinoma.And it is a useful ultrasonic feature for predicting thyroid microcarcinoma.