A lattice ordered group G is called (conditionally) orthogonally complete if each (bounded) disjoint subset of G has the supremum. Orthogonally complete 2-groups were investigated in several papers; cf. e.g., [l], [3], [6]. G is said t o be complete (o-complete) if each bounded subset (each bounded countable subset) of G has the supremum and the infimum. VEKSLER and GEJLER [ill have found necessary and sufficient conditions under which a conditionally orthogonally complete vector lattice is complete. The aim of this note is to show that if an 1-group G is conditionally orthogonally complete and o-complete, then it is complete. A particular case of this result (concerning singular Z-groups) was proved in [7]. Further we show that if G is archimedean and conditionally orthogonally complete, then the largest singular l-ideal of G is a direct factor of G. This generalizes a result of CONRAD and MCALLISTER [4]. S 1. Preliminaries For the basic notions and denotations concerning lattice ordered groups (Z-groups) cf. BIRKHOFF [2] and FUCHS [ 5 ] . The lattice operations are denoted by A, v and the group operation is written additively. Let G be an 1-group. For any subset X G put Xa = {YE G: lyl A 1x1 = 0 for each x E X ) .The set X' is called a polar of G. Each polar of G is a convex closed 1-subgroul) of G . For g E G we denote {g)6a = [g]; the l-group [g] is said to be a principal polar of G. A subset 1M & G will be called disjoint if m > 0 for each m E M and m i A m2 = 0 for any pair of distinct elements ml, m2 E M . A convex 1-subgroup A of G is said to be a direct factor of G if there exists a convex l-subgroup B of G such that A n B = 0 and A + B = G. If such 1-group B does exist, then it is uniquelly determined; namely, B = A'. This situation is denoted by writting G = A x B and B = A*. Then each g E G can be written