High resolution in vivo diffusion tensor imaging (DTI) within clinically feasible scan times is a challenging task. Multiple diffusion weighted (DW) images are needed to estimate the diffusion parameters and inherently, DW images have a low signal-to-noise ratio (SNR). Improving the SNR of the DW images by increasing the number of averages would require an infeasible long acquisition time. As a result, to ensure sufficient SNR, DW images are often acquired with a low spatial resolution, commonly 2x2x2mm³ - 3x3x3mm³, leading to large partial volume effects. One way to improve the trade-off between the spatial resolution, acquisition time and SNR is acquiring the data with an MRI scanner with stronger gradients (Human Connectome Project (HCP) scanner [1]) which allows a shorter TE and consequently a higher SNR. Complementary, recent developments in acquisition techniques, such as simultaneous multi-slice (SMS) [2], provide a significant reduction of the acquisition time. With the introduction of super-resolution reconstruction techniques for DTI (SR-DTI) [3, 4], high resolution DTI has become more feasible on MRI scanners with a regular gradient set. In this work, we propose to combine SR-DTI with SMS acquisitions (SMS-SR-DTI). This enables high resolution in vivo DTI within a clinically feasible scan time on a common MRI scanner.Four diffusion weighted (DW) data sets with voxel size 1.25x1.25x2.5 mm³ were acquired on a 3T clinical scanner with a common gradient set (80 mT/m, Prisma, Siemens, Erlangen Germany), using SMS echo-planar imaging (EPI) and an SMS factor of 3. Each data set was acquired with a different slice orientation, which was rotated around the phase encoding axis with incremental steps of 45°. Each of the four data sets consisted of 12 DW images (b=1000 s/mm²) and 2 non-DW images (b=0 s/mm²). One of the non-DW images was collected with reversed phase encoding blips. The diffusion gradient directions were sampled differently for each subset, leading to a total of 48 unique diffusion gradient directions. The overall scan time was 7min24. The acquired DW images were first corrected for EPI distortions by using reversed phase encoding correction [5, 6]. From the corrected DW images, high resolution DTI parameters were estimated on a grid with voxel size 1.25x1.25x1.25 mm³ using SR-DTI [3]. The motion was modeled within the SR-DTI model by an affine transformation, which was estimated using an iterative model based registration method [7]. To illustrate the high resolution of the resulting DTI parameters, DTI parameters were also estimated from high resolution HCP data and from low resolution data, both acquired in the same acquisition time as the SMS-SR-DTI data. From a pre-processed HCP data set (300 mT/m) with voxel size 1.25x1.25x1.25 mm³, 1 non-DW and 40 DW (b=1000 s/mm²) images were selected. The total acquisition time was 7min36. For the low resolution data, 2 non-DWI (one with reversed phase encoding) and 31 DW (b=1000 s/mm²) images with voxel size 2x2x2 mm³ were acquired. The acquisition time was 7min31. The images were corrected for EPI distortions prior to estimating the DTI parameters. From each DTI parameter set the directionally encoded color fractional anisotropy (DEC FA) was calculated.Figure 1 illustrates a transversal, coronal and sagittal slice of the DEC FA map for the low resolution data (fig 1a), the HCP data (fig 1b) and the SMS-SR-DTI data (fig 1c). Note that as each data set is acquired at a different scanner and from a different healthy volunteer, no direct quantitative comparison can be made between the different data sets. The SMS-SR-DTI map shows finer structures compared to the low resolution map. The SMS-SR-DTI map and the HCP map show a similar level of detail. This is for example clearly visible in the cerebellum (right column in figure 2). The left column of figure 2 shows a coronal zoom of the posterior region of corona radiate (pcr). In both the SMS-SR-DTI and HCP maps, the pcr, tapetum and superior longitudinal fasciculus (slf) can be delineated while in the low resolution map, the tapetum is not discernible from the pcr and slf due to large partial volume effects.SR-DTI was combined with an SMS acquisition to estimate DTI parameters with a high resolution from DW images acquired in a clinically feasible scan time. For a fixed acquisition time and with data acquired on an MRI scanner with weaker gradients, SMS-SR-DTI accomplishes a resolution visually similar to the HCP data. The use of SMS-SR-DTI opens up exciting possibilities for diffusion MRI in research and clinical routine.