Standard versions of Portuguese have two rhotic phonemes, which contrast only between vowels. In older Portuguese, these were the alveolar flap /ɾ/ (written ⟨r⟩) and the alveolar trill /r/ (written ⟨rr⟩). In other positions, only ⟨r⟩ is written, but it can stand for either sound, depending on the exact position. The distribution of these sounds is mostly the same as other Iberian languages like Spanish, i.e.:
- ⟨r⟩ represents a trill when written ⟨rr⟩ between vowels; at the beginning of a word; or following /n/, /l/, /z/, or /ʒ/. Examples: carro, rua, honrar, Israel.
- ⟨r⟩ represents a flap elsewhere, i.e. following a vowel or following any consonant other than /n/, /l/, /z/, or /ʒ/. Examples: caro, quatro, quarto, mar.
In the 19th century the voiced uvular fricative penetrated the upper classes in the region of Lisbon in Portugal as the realization of the trill. By the late 20th century, it had replaced the alveolar trill in most of the country's urban areas. In the rural regions, the alveolar trill is still dominant, but most of the country's population currently lives in or near the cities. The uvular trill is also heard sometimes.
The Setúbal dialect uses the voiced uvular fricative for all instances of "r" — word start, intervocalic, postconsonantal and syllable ending. This same pronunciation is attested in people with rhotacism and in non-native speakers of French origin.
In Africa, the classical alveolar trill is mostly still dominant, due to separate development from European Portuguese.
In Brazil, the normal pronunciation of ⟨rr⟩ is voiceless, either as a voiceless velar fricative, voiceless uvular fricative or a voiceless glottal fricative . In most dialects, this voiceless sound not only replaces all occurrences of the traditional trill, but is also used for all ⟨r⟩ that is not followed by a vowel (i.e. when at the end of a syllable, which uses a flap in other dialects). The resulting distribution can be described as:
- A flap only for single ⟨r⟩ and only when it occurs either between vowels or between a preceding consonant (other than /n/, /l/, /z/, or /ʒ/) and a following vowel. Examples: caro, quatro.
- A voiceless fricative or everywhere else: when written ⟨rr⟩; at the beginning of a word; at the end of a word; before a consonant; after /n/, /l/, /z/, or /ʒ/. Examples: carro, rua, honrar, Israel, quarto, mar.
In the three southernmost states, however, the alveolar trill remains frequent, and the distribution of trill and flap is as in Portugal. Some speakers use a guttural fricative instead of a trill, like the majority of Brazilians, but continue to use the flap before consonants (e.g. in quarto). Among others, this includes many speakers in the city of São Paulo and some neighbours cities, though alveolar approximant is also common, not only in the city, but the approximant is the dominant articulation in São Paulo state, the most populous state in Brazil. The caipira dialect has the alveolar approximant in the same position.
In areas where ⟨r⟨ at the end of a word would be a voiceless fricative, the tendency in colloquial speech is to pronounce this sound very lightly, or omit it entirely. Some speakers may omit it entirely in verb infinitives (amar "to love", comer "to eat", dormir "to sleep") but pronounce it lightly in some other words ending in ⟨r⟨ (mar "sea", mulher "woman", amor "love"). This tendency also occurs in some African countries; but speakers in Rio often resist the tendency, pronouncing a strong fricative or at the end of such words.
The voiceless fricative may be partly or fully voiced if it occurs directly before a voiced sound, especially in its weakest form of, which is normally voiced to . For example, a speaker whose ⟨rr⟩ sounds like will often pronounce surdo "deaf" as or even, with a very slight epenthetic vowel that mimics the preceding vowel.