A just-intonation tuning discovered in 1972 and published in 1978 by Heinz Bohlen, and discovered independently and published in 1984 by John Robinson Pierce, in which the 3/1 ratio (the pythagorean "perfect-12th", i.e., perfect-5th plus octave) is divided into 13 unequal steps. The equal-tempered version was published in 1978 by Kees van Prooijen.
The equivalence-interval of the Bohlen-Pierce scale is called the tritave.