Microalgal crusts of 12 desert plant communities distributed in 3 different stands in Wadi Araba and its tributaries  (Eastern Desert, Egypt) were involved in the present investigation. Four sites  were  selected in each stand. Soil crusts and samples were collected during March 2003, and some physico-chemical characters of these samples in addition to some biotic and abiotic factors were determined. A total of 92 algal species were recorded in all sites. Of these, 48 species belong to Cyanophyta, 20 to Chlorophyta and 24 to Bacillariophyta. The data revealed that the quantity and quality of microbiological algal crusts were governed by the type of the flowering plants as well as by the edaphic factors and physico-chemical characters of the soil.