Mr Quintana wants to meet representatives of several groups
The new UN human rights envoy for Burma is making his first visit there, days before the 20th anniversary of a failed uprising against military rule.
Special Rapporteur Tomas Ojea Quintana arrived in Rangoon late on Sunday for four days of meetings.
The UN envoy is keen to travel to areas hit by Cyclone Nargis. He could also hold talks with senior officials in the capital, Nay Pyi Taw, an official said.
Mr Quintana replaced Paulo Sergio Pinheiro, whose mandate ended in April.
According to a UN statement, the new envoy wished "to engage in a constructive dialogue with the authorities to improve (the) human rights situation of people of Myanmar (Burma)".
He has also asked to meet representatives of ethnic groups, political parties and NGOs, as well as travel to parts of the Irrawaddy Delta to see the effect of May's devastating cyclone, the statement said.
It is not clear whether he will seek a meeting with detained pro-democracy leader Aung San Suu Kyi.
But members of her National League for Democracy said they were keen to press him on the issue of better medical care for her.
The last time a UN rights envoy paid a visit to Burma was in November 2007, two months after troops used force to end large anti-government protests.
At least 31 people were killed and several thousand were detained.
In his report on the visit, then envoy Paulo Sergio Pinheiro said political and human rights activists had been targeted by the authorities.
The detainees were subjected to cruel and degrading treatment, he said.
Mr Quintana leaves Burma on Thursday, one day before the 20th anniversary of the 8 August 1988 mass protests during which at least 3,000 people are thought to have died.