Trial proceedings began with witnesses taking their oaths before presiding judge Thokozile Masipa.
State Prosecutor Gerrie Nel then read out the four charges against Pistorious, which include the alleged murder of his girlfriend on Valentine's Day last year at his Pretoria home.
He was also accused of shooting the roof of his ex-girlfriend's car, firing shots in a restaurant and possession of an unlicensed firearm.
"Do you understand the charges?" Judge Masipa asked Pistorious after they were read out. "And how do you plead?"
"Yes my lady," the sports superstar answered. "Not guilty my lady."
Pistorious says he shot at the bathroom door of his home, thinking an intruder had entered the house and not realizing his model girlfriend was inside.
Proceedings began earlier in Pretoria's Gauteng North High Court after being delayed by nearly two hours.
"Some court witnesses want to testify in Afrikaans [a West Germanic language spoken in South Africa and Namibia], so we're waiting for an interpreter," a court official told AA inside the packed courtroom.
Pistorious, accompanied by his uncle, had arrived earlier through the main court entrance, evading photojournalists and reporters who had expected him to come through the back entrance.
They came shortly after the arrival of the mother of Pistorious' late girlfriend, who had taken her seat in court.
Family and friends of the sports icon were seated in the front row of the courtroom, while Pistorious stood inside the dock.
"We're here to find out the truth of what happened to Reeva," Maria Nomufuna, a Pretoria resident attending the trial told AA. "Justice must prevail."
Nomufuna said that women had been victims of violence in South Africa and expected to see justice.
S. Africa court adjourns Pistorious trial to Tuesday
"The trial will continue tomorrow, starting at 9:30am," said presiding Judge Thokozile Masipa.
Pistorious has pleaded not guilty to all four charges leveled against him, including the murder of girlfriend Reeva Steenkamp on Valentine's Day of last year at his Pretoria home.
He was also accused of shooting the roof of his ex-girlfriend's car, firing shots in a restaurant and possession of an unlicensed firearm.
Pistorious says he shot at the bathroom door of his home, thinking an intruder had entered the house and not realizing his model girlfriend was inside.
Proceedings began earlier in the morning after being delayed by nearly two hours.
Pistorious, accompanied by his uncle, had arrived earlier through the main court entrance, evading photojournalists and reporters who had expected him to come through the back entrance.
They came shortly after the arrival of the mother of Pistorious' late girlfriend, who had taken her seat in court.
Family and friends of the sports icon were seated in the front row of the courtroom, while Pistorious stood inside the dock.
-Emotional testimony-
Michelle Burger, a University of Pretoria lecturer and a state witness, gave chilling descriptions of screams she reportedly heard on the night Steenkamp was killed.
The witness, who spoke a mixture of English and Afrikaans, one of South Africa's official languages, said she had never met the sports icon in person.
"I heard sounds of a woman screaming and I sat up in bed," said Burger, who lives roughly 170 meters from a complex bordering Pistorious's home, in which the murder is thought to have taken place.
She said the loud screams had also awakened her husband, who is also expected to provide witness testimony.
Burger said that her husband had gone to the balcony to determine the source of the noise while she had remained in bed.
"I also heard a male voice saying 'help, help, help'," she recalled.
"What I heard was very traumatic for me," the witness told the judge. "You could hear blood curdling screams."
"My husband returned from the balcony," Burger added. "I was still in bed. I said I hoped that that woman had not seen her husband killed."
Popularly known as the "Blade Runner," Pistorious was born without the fibulas in both of his legs. Before completing his first year, he had to have both his lower limbs amputated.
In 2004, he rose to fame at the age of 17 after winning a gold medal at the Athens Paralympics Games.
The sprinter has since gone on to win several other medals.
Pistorious made history in 2012 by becoming the first amputee runner to compete in the Olympics.
