In Roumania, the first studies on the effect of the rhizosphere on tobacco plants at all stages from the seedbed were made by the authors in 1993. In Roumania, tobacco seedlings are produced using a nutritive mixture made of fermented manure, soil and sand in proportion of 1 : 2 : 1. In the study on the rhizosphere and edaphosphere of tobacco plants, a nutritive mixture gradually impoverished, made of soil and sand only, was used. For the microbiological analysis of the rhizosphere the following method was used. The largest part of the soil was removed and at least 10 grams of the soil that stuck to the root was collected separately, and seven successive dilutions made out of it. Six dilutions were made out of the edaphosphere. The dilutions were added to the topping medium, beginning with the fifth dilution for the rhizosphere and fourth dilution for the edaphosphere. For the subsequent bacterial colonization only the dilution where the colonies were the fewest (from ten to approximatively 200 per plant) was used. In addition, a superficial spreading was applied, from dilutions 5 and 6 for the rhizosphere and 4 and 5 for the edaphosphere. A microscope observation of the edaphosphere after 7 days of development of the colonies showed a division in sporogenic bacteria and, eventually, actinomicetes. For fungi, inoculation was made with soil drops and the index of colonization by species of micromicetes was determined for both the rhizosphere and edaphosphere. It was found that the highest value of the ratio R : S (rhizosphere : edaphospere), of 1.60, was recorded for the nutritive mixture made of 75% soil and 25% sand. The most frequent species of bacteria in the rhizosphere were Arthrobacter sp. (680 x 106) and Pseudomonas fluorescens (51 x 106). In the edaphosphere the most frequent species of bacteria was Arthrobacter sp. (48 x 106).