In this paper we study progressive filtration expansions with càdlàg processes. Using results from the theory of the weak convergence of σ-fields, we first establish a semimartingale convergence theorem. Then we apply it in a filtration expansion with a process setting and provide sufficient conditions for a semimartingale of the base filtration to remain a semimartingale in the expanded filtration. Applications to the expansion of a Brownian filtration are given. The paper concludes with applications to models of insider trading in financial mathematics. * Let D be the space of càdlàg 1 functions from [0, T ] into R. Let Λ be the set of time changes from [0, T ] into [0, T ], i.e. the set of all continuous strictly increasing functions λ : [0, T ] → [0, T ] such that λ(0) = 0 and λ(T ) = T . We define the Skorohod distance as follows d S (x, y) = inf λ∈Λ ||λ − Id|| ∞ ∨ ||x − y • λ|| ∞for each x and y in D. Let (X n ) n≥1 and X be càdlàg processes (i.e. whose paths are in D), indexed by [0, T ] and defined on (Ω, H, P ). We will write X n P → X when (X n ) n≥1 converges in probability under the Skorohod J 1 topology to X i.e. when the sequence of 1 French acronym for right-continuous with left limits