Cells in the mammalian brain tend to be grouped together according to their afferent and efferent connectivity, as well as their physiological properties. The columnar structures of neocortex are prominent examples of such modular organization, which has been studied extensively in anatomical and physiological experiments in rats, cats and monkeys. The importance of noninvasive study of such structures, in particular in human subjects, cannot be overemphasized. Not surprisingly, therefore, many attempts were made to map cortical columns using functional magnetic resonance imaging (fMRI). Yet, the robustness, repeatability, and generality of the hitherto used fMRI methodologies have been a subject of intensive debate. Using differential mapping in a high magnetic field magnet (7 Tesla), we demonstrate here the ability of Hahn Spin-Echo (HSE) BOLD to map the ocular dominance columns (ODCs) of the human visual cortex reproducibly over several days with a high degree of accuracy. In contrast to the conventional Gradient-Echo (GE) Blood oxygen level dependent (BOLD) imaging, which systematically failed to resolve ODCs in the vicinity of large vessels, HSE signals uniformly resolved the ODC patterns, providing an unconstrained mapping methodology that can be - in principle - used in any cortical area, the columnar organization of which is not a priori known. Furthermore, the methodology reported here can be utilized to map areas (e.g. fronto-temporal cortices), whose visualization is typically masked by susceptibility artifacts, and it paves the way both for the study of the functional architecture of the human sensory cortices, and of the brain modules underlying specific cognitive processes. Conclusions In this study, we demonstrate that columnar level mapping in human visual cortex can be robustly obtained at high magnetic fields together with HSE BOLD fMRI and differential imaging. When applying the commonly used and conventional GE BOLD imaging, it is necessary that non-specific responses from large vessels are cleanly subtracted out, leaving only highly specific signal sources. This assumption is not generally valid under conditions that maximize the stimulus response as employed in this study. Not surprisingly, therefore, highresolution GE BOLD studies in humans (Cheng et al., 2001; Goodyear and Menon, 2001; Menon et al., 1997) have shown limited degree of reproducibility and generality across subjects. The degree of reproducibility in this high-field study was high for both the GE and the HSE functional maps, albeit with distinctly different spatial contents. The HSE maps depicted fine and more predictable ODC maps across different subjects, in structures that are consistent with previous anatomical data from humans and functional data from monkeys. In contrast, the GE maps showed coarser structures that less resembled the expected ODC maps. The unpredictable nature of the GE maps depends highly on the location of large vessels relative to the imaged gray matter areas. The use of HSE BOLD imaging in humans in the general case may prove highly advantageous at high magnetic fields for mapping of columnar structures, especially when single condition designs are of importance.