Water soluble FeOOH nanospindles with small size were synthesized by a simple hydrolysis method of inorganic salts and water bath treatment with different incubation time. The morphology, microstructure, magnetic resonance imaging (MRI) performance and cytotoxicity of the as-prepared FeOOH nanospindles were investigated, respectively. The results showed that the longitudinal length of FeOOH nanospindles was about 40-50 nm, and the incubation time had important effect for the morphology and production rate of FeOOH nanospindles. MRI test showed that the longitudinal and transverse relaxivities (r(1) and r(2) values) of FeOOH nanospindles were about 3.06 mM(-1) s(-1) and 5.06 mM(-1) s(-1), respectively. Furthermore, the experimental results of the Prussian Blue staining showed the clusters of FeOOH nanospindles in the cytoplasm of the labeled cells, and the cytotoxicity characterization indicated that FeOOH nanospindles have low cytotoxicity. Therefore, the as-prepared FeOOH nanospindles will have potential applications as T-1- and T-2-weighted MRI contrast agents. Crown Copyright (C) 2011 Published by Elsevier B.V. All rights reserved.