The utilization of micro-algae for the production of food and fine chemicals is growing in importance. However, confusion of names and species makes comparison of results by different authors very difficult. In this work, five species of Dunaliella were characterized using their 18S ribosomal RNA genes. Conserved oligonucleotides complementary to 5' and 3' termini of the 18S rDNAs were designed and utilized to amplify theme, restriction fragment length polymorphism analysis of the polymerase chain reaction products was developed. Species-specific primers were also designed and utilized to corroborate the identification.