title: Erratum.
abstract: In the report by K. Denniston-Thompson et al., entitled "Physical structure of the replication origin of bacteriophage lambda" (9 December 1977, pp. 1051-1056), the T.A base pair at position 1426 (Fig. 6) should be an A.T base pair; also the position of the G.C base pair affected by the til2 mutation should be 1453 rather than 1451.