Modern neurocritical care units generate high volumes of data. This data is originates from a multitude of devices in various formats and levels of granularity. We present a new data format intended to store this data in an ordered and homogenous way. The adopted data format was built on the hierarchical model based on the HDF5 format capable of dealing with a mixture of small and very large data sets with equal ease. It is possible to access and manipulate individual data elements directly within a single file and is extensibile and versatile. Excellent compression is possible and comprehensive support exists for platforms including MATLAB, R and Python. The new file format was implemented in ICM+ software and validated as part of the CENTER-TBI project where it has been used to storage all acquired ICU monitoring data from the participating centres across Europe. Keywords: HDF5, Multimodal monitoring, Data storage, Data format