Climatization of the Viking and medieval collections of Oslo University, including storerooms and conservation department, began in 1960. Today, three coherent exposition-rooms of approximately 1600 cubic meters total are controlled by three Defensor 4000 V humidifiers. Records for 1980 show long cycle (yearly) variations between 40% and 60% relative humidity, and short cycle (daily) variations of 2%-3% relative humidity. These conditions are considered acceptable. Polychrome wood and iron objects require different relative humidity levels, calling for a physical separation of the exposition-rooms. -- AATA