Marchers turned out in the heat and pouring rain with the usual array of demands, but two key issues predominated: a desire for genuine universal suffrage and for Beijing to keep to its promise of "one country, two systems".
Angered by the State Council's white paper declaring its "comprehensive jurisdiction" over the city, and by the dysfunctional legislature, some also said they would join the overnight sit-in by student activists.
Despite torrential downpours, swarms of protesters continued pouring into the clogged streets through the afternoon and evening.
"The rain will not put me off," marcher Raymond Chan said.
A handful of marchers pushed against police barricades but the rally was largely peaceful, and a carnival atmosphere prevailed.
Artist Kacey Wong and a few others, dressed as police officers and wearing vests bearing the word "politics", held up humorous warning signs mocking police for arresting peaceful protesters at previous rallies.
An artist had made a cardboard "white paper" bigger than a car, which he lashed with ropes to express his discontent with Beijing's recent edict on Hong Kong's autonomy.
Some sang a Cantonese song based on the tune "Can you hear the people sing?" from the musical adaptation of Victor Hugo's novel . The song, with rewritten lyrics referring to universal suffrage, has become an anthem for Hong Kong protesters.
One marcher wore sieves on his head, a reference to the government's insistence any electoral reform must include pre-screening of candidates in the chief executive election.
Echoing that sentiment, Lee Yiu-sun, 52, said he could not accept any electoral reform proposal that enabled the screening of candidates.
"We own the place. Why should we beg the government to give us what we want, bit by bit?" Lee, a sports coach, said.
He said he would join the students in Chater Road after the march, because, "the young ones have no bargaining power. I must stand by them".
Also sympathetic was Anson Chan Fang On-sang, the former chief secretary, who joined the march with members of her think tank Hong Kong 2020.
"I appreciate the students' courage but I call for restraint on all sides," she said.
Another former minister, Joseph Wong Wing-ping, who joined the march for the second time, said he was supporting freedom of expression after the cyberattack on Occupy Central's online "referendum". He had also been upset by the white paper.
Sharing their concerns for democracy were pop singers Anthony Wong Yiu-ming and Denise Ho Wan-si, both of whom have come out as homosexual and are vocal on political issues.
"We need to stand out and tell the government that we need real universal democracy," Wong said. "No one wants to go as far as to occupy Central, but it'll be a special measure at a special time."
Another hot topic was the plan for two new towns in the northeastern New Territories, preliminary funding for which was recently, and controversially, approved by the Legislative Council's Finance Committee.
Tom Shum, 40, said he did not come to the annual protest every year but the fiasco in Legco had prompted him this time. "It's not the way that Hong Kong works - it's not how Legco works," the advertising worker said.
Among the crowd were activists from Macau, Taiwan and the mainland. A29-year-old member of the underground Enhancing Civil Rights Party of China founded in Guangzhou said he hoped Hong Kong could preserve its high degree of autonomy and remain an example for the mainland to achieve democracy.
Mr Sham, a restaurant owner in Causeway Bay, set up a booth selling chilled bottled water and soya bean milk. "I don't care about how much business I do today, I just want to give a helping hand to the marchers," he said.
Joyce Ng, Lo Wei, Fanny Fung, Johnny Tam, Jennifer Ngo, Shirley Zhao, Phila Siu, Emily Tsang, Jeffie Lam, Danny Lee. Additional reporting by Associated Press, Agence France-Presse