On some seaweeds collected on the Straits of Messina and off the Sicilian coasts. – 2 Phaeophyceaeof the ordinesDictyotalesandDesmarestialesand 17Rhodophyceaeof the ordinesCryptonemiales, GigartinalesandCeramialesare collected for the first time in the Mediterranean Sea (forDesmarestia ligulata) or in some localities off the Sicilian coasts and off the circumsicilian isles. For each species systematic and distribution data are reported.