The objective of this study was to determine the identity of viruses affecting tobacco in Caceres, Spain as well as their incidence and distribution. Sixty fields of flue-cured and twenty fields of Burley tobacco were sampled in 1990 and 1991 in the main tobacco production areas. The number of fields evaluated/area was proportional to the tobacco produced in that area. Fields within areas were selected at random. Percentage of plants infected (incidence) was determined on 1,000 plants/field based on symptomatology. Samples were collected representing all symptom types observed in each field and were then inoculated on seedlings of cultivar Burley 21 in the greenhouse. The Ouchterlony double diffusion test was subsequently used to determine virus identity. The main viruses identified were : cucumber mosaic virus (CMV), tobacco mosaic virus (TMV), and potato virus Y (PVY). Incidences of these viruses averaged over years were : CMV = 2% on flue-cured and 4.1% on Burley ; TMV = 20.8% on flue-cured and 0.8% on Burley; PVY = 20.6% on flue-cured and 29.8% on Burley.