C-ORAL-BRASIL I is a Brazilian Portuguese spontaneous speech corpus compiled following the same architecture adopted by the C-ORAL-ROM resource. The main goal is the documentation of the diaphasic and diastratic variations in Brazilian Portuguese. The diatopic variety represented is that of the metropolitan area of Belo Horizonte, capital city of Minas Gerais. Even though it was not a primary goal, a nice balance was achieved in terms of speakers' diastratic features (sex, age and school level). The corpus is entirely dedicated to informal spontaneous speech and comprises 139 informal speech texts, 208,130 words and 21:08:52 hours of recording, distributed into family/private (80%) and public (20%) contexts. The LR includes audio files, transcripts in text format and text-to-speech alignment (accessible with WinPitch Pro software). C-ORAL-BRASIL I also provides transcripts with Part-of-Speech annotation implemented through the parser system Palavras. Transcripts were validated regarding the proper application of transcription criteria and also for the annotation of prosodic boundaries. Some quantitative features of C-ORAL-BRASIL I in comparison with the informal C-ORAL-ROM are reported.