The first successful Agrobacterium-mediated transformation of the green alga Haematococcus pluvialis Flot. using the binary vectors hosting the genes coding for GUS (b-glucuronidase), GFP (green fluorescent protein), and hpt (hygromycin phosphotransferase) is reported here. Colonies resistant to hygromycin at 10 mg Æ L)1 expressed b-glucuronidase. The greenish yellow fluorescence of GFP was observed when the hygromycin-resistant cells were viewed with a fluorescent microscope. PCR was used to successfully amplify fragments of the hpt (407 bp) and GUS (515 bp) genes from transformed cells, while Southern blots indicated the integration of the hygromycin gene into the genome of H. pluvialis. SEM indicated that the cell wall of H. pluvialis was altered on infection with Agrobacterium. The transformation achieved here by Agrobacterium does not need treatment with acetosyringone or the wounding of cells. A robust transformation method for this alga would pave the way for manipulation of many important pathways relevant to the food, pharmaceutical, and nutraceutical industries.