A mt(-) (male) mutant cell of Chlamydomonas reinhardtii was isolated. It was reduced in size and showed few chloroplast (cp) nucleoids. When smaller mutant cells, obtained through a 3 mu m pore filter, were crossed with mt(+) wild type cells, the frequency of transmission of cp genes was not different from the wild type cross. The cell size and the number of cp nucleoids appear to have no effect on the transmission of cp genes.