Due to the increased pressure on some of the established fungicides used in wood preservation, possible alternative products become more interesting. The requirements for new chemicals are mainly lower toxicity and greater environmental acceptability. However the efficacy to target organisms should be as good as that of the currently used ones, preferably better. A possibility for progress in this direction could be fungicidal combination products showing broader spectrum of efficacy and synergistic effects. Mixtures of tributyltin compounds with Furmecyclox and K-HDO respectively are tested for this purpose. Toxic values with and without artificial ageing (wind-tunnel exposure and leaching) were determined. Investigations have been made with coating-formulations in order to test penetration, evaporation and the influence of UV-radiation. Aqueous formulations were tested for special purposes such as the treatment of freshly cut timber and the protection of brickwork. The results obtained are very promising, especially regarding long term durability. Further investigations mainly with the aqueous formulations including other test fungi and field trials are necessary to confirm the suggested application as wood preservatives.