This paper examines the systemic functional description of Spanish Nuclear Transitivity as proposed by Lavid, Arús and Zamorano (2010) and proposes two modifications to their system network.The first is to reevaluate their concept of 'causation', which is limited to 'lexical ergativity' (He broke the window/The window broke).It is argued that causation can be realized with a range of structures that include analytical (He made the boy run) and synthetic (He chased the boy) versions.Furthermore, lexical ergativity is subdivided into 'Instigation' (He broke the window) and 'Initiation' (He rolled the ball).These options are considered more 'delicate' choices of the 'effective voice' subsystem.The second modification is the inclusion of the ER-participant (Actor, Carrier, Sayer, Behaver, Senser) explicitness system, which is exclusive to Spanish.This set of options allow the speaker to present crucial participants in Agent•Process•Medium and Medium•Process configurations obliquely.Although the different realizations of this system ('se' passives, periphrastic passives, impersonal 'se' and impersonal 3 person plural), have been widely discussed in the literature from both systemic and non-systemic perspectives, these had not been mapped into the system network of Spanish Transitivity.