The cause of death was a rare and aggressive cancer, according to doctors at the Stanford Cancer Center.
She "was gracious, generous, unassuming and selfless," noted her niece, Pam Giannotti.
"Harriet's love, devotion to and support of the children and families we care for at Lucile Packard Children's Hospital has been critical for our being able to offer the best care today, and to ensure even better children's health in the future," said Dr. Harvey Cohen, the hospital's former chief of staff.
In Woodside, Ms. Zelencik joined what is now named the Allied Arts Guild Auxiliary as well as the Woodside Hills Garden Club. The guild provides support for the children's hospital through the Lucile Packard Foundation for Children's Health.
Several times, with great success, she chaired the guild's principal fundraising event, Tally Ho. "She was perpetually, in her gentle and selfless way, a wonderful support to all of the auxiliary's activities," noted Barbra Wood, a former president of the organization.
And, Ms. Zelencik got her husband involved with the guild. In 1993 the Zelenciks developed a special project fundraising initiative designed to increase support of the hospital from local companies. Victoria Applegate, of the foundation, said the fund to finance specific items of need at the hospital, introduced by the Zelenciks, "has been exquisitely successful over the years."
Those who knew Harriet Zelencik saw a woman of power, family members said. She was slightly taller than 5 feet and never weighed more than 105 pounds. Yet, as one friend of more than 40 years noted, "she had more power, determination and stamina than most twice her size."
"She never smoked, and always drank the best wine we could afford," noted her husband. She loved dogs, especially big ones like the Pyrenees mountain dogs, Spook and Sparky, who graced their yard over the years. "She always wanted dogs bigger than she was."
She was born in October 1935 in East Chicago, Indiana, the youngest of the 11 children of Jacob and Mary Sarnecki.
She met her future husband when they both were working at the Youngstown Sheet and Tube Co., she as an accountant, and he in the mail room, a summer job while going to school. They were married in 1958 while he was still at Purdue University, from which he graduated in 1960 with a degree in electrical engineering.
In 1964 they moved to Granada Hills, where she and their daughter, Mary, who was born while they were at Purdue, developed a love of horses and riding. When they moved to Woodside, easy access to horses was essential, Steve Zelencik said, although Harriet refused to house horses at her home. "I don't mind going to the barn," she once told her husband, "but we're not going to have the barn on our property."
Their daughter, a real estate agent, died unexpectedly in 1994.
Mr. Zelencik was a longtime executive in the semiconductor industry. Following five years at Fairchild Semiconductor, Mr. Zelencik in 1970 joined the fledging Advanced Micro Devices company, where he stayed for 30-plus years, retiring as the senior vice president of sales and marketing.
W.J. Sanders III, founding chief executive officer of AMD and a friend of the Zelenciks for more than 40 years, said: "People like Harriet allow people like Steve to go out into the world and do great things. She provided the rock-solid base camp so Steve could go out and climb mountains."
In addition to her husband, Ms. Zelencik is survived by her brothers, Walter and Louis Sarnecki of northern Indiana; her mother-in-law, Catherine Zelencik, who is 102; and sister-in-law, Mary Schmidt, both of Santa Barbara, and multiple nieces and nephews and other relatives.
Gifts in her memory can be made to the Harriet and Mary Zelencik Fund for Pediatric Research at Lucile Packard Children's Hospital and sent to Tara Quinn, Lucile Packard Foundation for Children's Health, 400 Hamilton Ave, Ste 340, Palo Alto, CA 94301 or online at LPFCH.org.
Services will be private.