<jats:title>Abstract</jats:title><jats:p>The antitumor antibiotic ‘rubiflavin’ was investivated. It was shown to be a mixture of several compounds, nine of which ‐ after isolation by HPLC ‐ could be identified by <jats:sup>1</jats:sup>H‐NMR spectroscopy. The rubiflavins A (<jats:bold>4</jats:bold>), B (5), C‐1(<jats:bold>6</jats:bold>), C‐2(<jats:bold>7</jats:bold>), D(<jats:bold>8</jats:bold>), and E(<jats:bold>9</jats:bold>) are pluramycin antibiotics differing only in their side chains at C(2). Rubiflavin B(5) was found to be identical with kidamycin, rubiflavin F(<jats:bold>10</jats:bold>) with isokidamycin. Two unpolar compounds isolated which lack the two sugar rings typical for pluramycin antibiotics were called rubiflavinone C‐1 (<jats:bold>2</jats:bold>) and C‐2 (<jats:bold>3</jats:bold>); they are the ‘aglycones’ of the corresponding rubiflavins.