The "Giara di Gesturi" is a basaltic plateau placed in the central-southern part of Sardinia Island. The present study involves the algal flora of seven ephemeral ponds named “Paulis” present in the Giara. A total of 213 algal taxa were identified, distributed as follows in the different classes: Cyanophyceae: 16; Xanthophyceae: 1; Bacillariophyceae: 110; Dinophyceae: 4; Euglenophyceae: 10; Chlorophyceae: 42; Klebsormidiophyceae: 2; Zygnematophyceae: 28. From a qualitative point of view the Bacillariophyceae clearly predominate. The high biodiversity of these environments shows the extreme importance of the ephemeral pools in the Mediterranean environment. This preliminary study proves to be extremely promising and further researches are to be hoped.