A ring R with unity is called a (quasi-) Baer ring if the left annihilator of every (left ideal) nonempty subset of R is generated (as a left ideal) by an idempotent. Armendariz has shown that if R is a reduced Pi-ring whose centre is Baer, then R is Baer. We generalise his result by considering the broader question: when does the (quasi-) Baer condition extend to a ring from a subring? Also it is well known that a regular ring is Baer if and only if its lattice of principal right ideals is complete. Analogously, we prove that a biregular ring is quasi-Baer if and only if its lattice of principal ideals is complete.Throughout R will denote a ring with unity, B ( # ) its set of central idempotents, Cen (R) its centre, Z T {R) and Zi(R) its right and left singular ideals, respectively. All subrings have a unity which may not coincide with the unity of the overring. The word "ideal" used alone (that is, without the adjectives "left" or "right") means a two-sided ideal. Recall from [19] that R is a Baer ring if the right annihilator of every nonempty subset of R is generated (as a right ideal) by an idempotent. The study of Baer rings has its roots in functional analysis [3] and [19]. In [19] Kaplansky introduced Baer rings to abstract various properties of von Neumann algebras and complete regular *-rings. The class of Baer rings includes the von Neumann algebras (for example, the algebra of all bounded operators on a Hilbert space), the commutative C* -algebras C(T) of continuous complex valued functions on a Stonian space T, and the regular rings whose lattice of principal right ideals is complete (for example, regular rings which are right continuous or right self-injective). Also the Sherman-Takeda theorem [24] and [28] shows that every C* -algebra has a universal enveloping von Neumann algebra (hence a Baer ring).In [12] Clark defines a ring to be quasi-Baer if the left annihilator of every ideal is generated (as a left ideal) by an idempotent (equivalently, the left annihilator of every