We propose that the order Prochlorales Florenzano, Balloni, and Materassi 1986 (emend. Burger-Wiersma, Stal, and Mur 1989), the family Prochloraceae Florenzano, Balloni, and Materassi 1986, and the family Prochlorotrichaceae Burger-Wiersma, Stal, and Mur 1989, validly published in the International Journal of Systematic Bacteriology under the rules of the Bacteriological Code, be rejected because of the imperfection of ordinal diagnosis. The oxygenic-phototrophic prokaryotes involved are proposed to be incorporated under their validly published names into the orders Chroococcales and Oscillatoriales of the 'Cyanobacteria' group. Correspondingly, the latter is proposed to be upgraded to equal 'Oxygenic photosynthetic bacteria' (Section 19 in Bergey's Manual).