A protester shouts slogans ahead of the rally in Hong Kong
Pro-democracy activists in Hong Kong have returned to the streets for their first big rally since mass protests last year.
A large police presence was in force to deter protesters from reoccupying key areas of Hong Kong.
But protesters were not reported to be planning a repeat of the occupations that shut down parts of the city.
Last year's Occupy demonstrations called for fully democratic elections for the territory's chief executive.
China has promised the semi-autonomous territory direct elections in 2017, but ruled that candidates had to be vetted by Beijing.
Analysis: Carrie Gracie, BBC China editor
How many marchers can Hong Kong's pro-democracy movement muster on the streets? Two months after police cleared the encampment from the heart of the city, today is an important test of strength for a movement which caught the world's attention last September with its youthful energy and idealism but which has since struggled to maintain a united voice and popular support.
From the point of view of the demonstrators, the fundamental question is whether Hong Kong's political destiny will be defined by its own citizens or by authoritarian rule from China.
The guarantees of a high degree of autonomy under the "one country, two systems" formula are being put to the test as political controls on the mainland tighten and Hong Kong's economic leverage diminishes.
Tens of thousands started taking to the streets in September 2014, demanding change.
There were violent clashes with police, and the final protest camp was dismantled in December.
One organiser, Daisy Chan, told the AFP news agency the latest protest would show last year's demonstrations were a watershed for Hong Kong.
"In the past years, these citizens were less political than they are right now. The Occupy movement woke people up.
Organisers hope up to 50,000 people will attend Sunday's pro-democracy rally
"The rally continues to call out to people to join the democracy movement."
However, Lam Woon-kwong of the Executive Council, Hong Kong's top policy-making body, told local radio on Sunday: "You can't threaten the central authorities."
The numbers attending will give a sense of the stomach left for the fight in Hong Kong, the BBC's John Sudworth says.
About 2,000 police officers were expected to oversee the event, the South China Morning Post reported.
Police were wary of reports that there were no plans for protesters to reoccupy public areas, issuing a statement saying: "It is believed that those supporting the illegal occupation are likely to seize the opportunity to reoccupy roads which have been now reopened to traffic."
The umbrella became a symbol of the protests last year