We prove that if T is a theory of large, bounded, fields of characteristic 0 with almost quantifier elimination, and T D is the model companion of T ∪ {"∂ is a derivation"}, then for any model (U , ∂) of T D , differential subfield K of U such that C K |= T , and linear differential equation ∂Y = AY over K, there is a Picard-Vessiot extension L of K for the equation with K ≤ L ≤ U , i.e. L can be embedded in U over K, as a differential field. Moreover such L is unique to isomorphism over K as a differential field. Likewise for the analogue for strongly normal extensions for logarithmic differential equations in the sense of Kolchin.Recent papers such as [2] and [5] have shown that under certain conditions (on the differential field (K, ∂) and its field C K of constants), given a linear differential equation over (K, ∂) we can find a Picard-Vessiot extension (L, ∂) of (K, ∂) for the equation such that C K is existentially closed in L (as a field). Among the motivating examples to which this applies is the case where C K is * 2. A field K is said to be large (or ample) if for any algebraic variety V which is defined over K, is K-irreducible, and has a nonsingular K-rational point, V (K) is Zariski dense in V .Remark 1.2. 1. Large fields were introduced by Pop in [13] where one can find other characterizations.2. The class of large fields is elementary in the language L.