Jenny Rose Ng's daughters weren't even 10 years old when they came home to their flat in the Melbourne suburb of Richmond and found their mother stabbed to death in 1982.

She'd been stabbed a "significant number of times", with her 11-month-old daughter in the next room, laying in her bassinet unharmed.

Now just before the 36th anniversary of Ms Ng's death, Victoria Police is offering a $1 million reward to find whoever killed her.

Detective Inspector Tim Day said this is one of those cases that risks "sliding into the abyss forever".

"It's never too late to tell us what you know," he said.

"Any piece of information, no matter how insignificant you might consider it to be, could be exactly what investigators need."

Ms Ng, 39, was separated from her husband at the time of her death and was taking care of her four children and her parents who lived nearby in Kew.

She was last seen alive on the morning of April 23, 1982, helping her daughters, aged nine and seven, and her 11-year-old son get ready for school.

They all left home about 8:30am and she was found dead when her daughters returned home for lunch about 12:30pm.

Ms Ng, 39, was murdered in her Richmond flat in 1982. ( Supplied: Victoria Police )

After an extensive investigation, police established that a man entered Ms Ng's flat about 10:30am, but that man has never been identified.

"For her children to come home and find her murdered is almost beyond contemplation," Detective Inspector Daly said.

"We still don't know why Jenny was murdered and we're hoping by announcing this reward today, we will get information that leads to detectives finding out who is responsible.

"They've had 36 years to live with this information and [to have it] sit on their conscience."

Her son, Jim (not his real name), said he was lucky to have 11 years with his mother before she died.

"Only of my fondest memories is something we took for granted as a family — her waking us up in the morning for school," he said.

"We choose to remember the better parts, rather than the tragedy.

"It's part of my growing up and my childhood, it's part of my history."

Jim said the family was seeking closure but they also want to know why.

"Closure's one aspect but we don't have an understanding of why, why her, why was it as horrific as it was," he said.

"That's the most challenging [thing].

"She was a devoted mother, a strong independent woman trying to bring up a family on her own."