Reactor issues such as thermal maldistribution and high pressure drop are indicators that a refinery may be failing to capture the maximum value from a hydroprocessing unit. Fortunately, a low-cost revamp involving the installation of the latest-generation reactor internals can usually address such issues. These include high-dispersion trays, which help to prevent thermal maldistribution by achieving near-perfect wetting and ultra-uniform utilisation of the catalyst, antifouling trays designed to reduce pressure drop buildup, quench internals for uniform process and quench mixing at the interbeds, catalyst support grids, ultra-low bottom baskets and speciality devices to accommodate the elevations that may be required for bed optimisation. When installing the latest-generation reactor internals, there are often opportunities to capture additional value. For instance, depending on the axial temperature gradient, it could be possible to combine beds to increase catalyst uptake. And, when the quenches, bottom baskets and filter trays are designed to occupy minimal reactor volume, they can enable more catalyst to be loaded into the reactor. This can be used to help extend the catalyst cycle life, lower the weighted average bed temperature (WABT), increase the throughput or process heavier, less-expensive feedstock, which results in a higher margin. In some cases, the unit yields can be redefined for better economics. In addition, some latest-generation reactor internals are designed for fast removal and installation, which can help to increase days on stream and can be worth significant revenue. There also are safety advantages, such as far less confined space residence time, because cutting and welding are not required and manways are large to enable fast entry and exit. In some cases, no inert entry is required to get access to the bed. This paper will discuss many of the most common issues encountered in a ydroprocessing reactor and, through the inclusion of case studies, explain how the latest-generation reactor internals can help to resolve them