This article presents the results from an analysis of the politeness strategies used by Spanish native speakers in their L1 (Castilian) to express different speech acts: request, denial, instruction, complaint and mandate. The analysis was carried out using a Discourse Completion Test (DCT). Respondents were asked to fill in different sentences from a silent animated short film. Respondents were also asked to associate the degree of cordiality of each scene to the sentences they provided. Once the data was collected, the differences in the formulation of the speech acts were analysed together with the assigned degree of politeness. The results, which may also apply to SFL teaching, show a relationship between the identified degree of politeness and the discursive strategies used, and it also confirms the adoption of expressive strategies and procedures already identified by the scientific literature. Key words: pragmatics, politeness, DCT, SFL.