A study of the algal flora from surface sediments and from the littoral of the northern basin of Lake Tanganyika, revealed 365 diatom taxa. Most of these taxa have already been included in an earlier published check-list on the algal flora of the East African Great Lakes (Cocquyt et al. 1993). Diatom analyses were carried out on 327 samples from several localities in the northernmost part of the lake, up to Nyanza-Lac in the south of Burundi. A short description is given of all the sample stations and of the investigated samples (collection A. Caljon, University of Ghent). The present publication gives a systematic account of the observed diatom taxa. We must remark, however, that many described taxa need further investigation. Apart from the distribution, all earlier reports of each taxon in Lake Tanganyika are given. A great number of the species are represented by original microphotographic pictures or original drawings.