Vowel opening and spectral emphasis are investigated as possible acoustic correlates of secondary stress in Brazilian Portuguese. F1 and energy difference between frequency bands were measured for vowel /a/ in five- and six-syllable stress groups. Results for F1 indicate greater opening for vowels in initial and stressed positions. As for the spectral feature, relative emphasis in bands B2 (0.5 to 1 kHz) and B4 (2 to 4 kHz) has some relevance to phrase stress signaling, but not to secondary stress if it is to be equated to binary alternations.