In the refining of crude oil, hydroprocessing units such as hydrotreaters and hydrocrackers are used to remove impurities such as sulfur, nitrogen, and metals from the crude oil. They are also used to convert the feed into valuable products such as naphtha, jet fuel, kerosene and diesel. The current invention provides very high to total conversion of heavy oils to products in a single high-pressure loop, using multiple reaction stages. The second stage or subsequent stages may be a combination of co-current and counter-current operation. The benefits of this invention include conversion of feed to useful products at reduced operating pressures using lower catalyst volumes. Lower hydrogen consumption also results. A minimal amount of equipment is employed. Utility consumption is also minimized.