Those years were among the most productive of his life, said his daughter, Maria.
His training included a bachelor's degree from the University of Puerto Rico and a master's from Columbia University, both in psychology.
Mr. Montalvo helped shape the field of family therapy and inspired clinicians with his brilliance, his eloquence, and his insistence that cultural minorities who came to him for care receive equal treatment with all other patients, his family said in a tribute.
"Equal treatment means equal treatment on all levels," he told his daughter. He saw positive cultural norms as a resource and a way to strengthen families.
From the mid-1950s to the early 1960s, he collaborated with eminent family therapist Salvador Minuchin at Wiltwyck School for Boys in Harlem. The two developed structured ways of looking at - and addressing - personal problems by examining how the individual functions within the family. Unheard of then, the methods are in wide use today.
The collaboration produced the book Families of the Slums, a 1967 clinical study of low-income urban families that is a resource for mental-health providers.
"Anything I wrote during the years we worked together had been part of a dialogue with him, in which he edited and enriched my ideas," Minuchin wrote in a tribute.
Likening Mr. Montalvo to "a twin brother," Minuchin wrote: "He has the rare ability to look at the most complex and hopeless human situation, and find possible solutions."
As senior supervisor at the Child Guidance Clinic, Mr. Montalvo developed the first family-therapy video library, producing films such as A Family With a Little Fire and Constructing a Different Reality. The videos are used as training tools for therapists.
In the mid-1980s, Mr. Montalvo cowrote The Difficult Divorce, published in 1986. In it, he and two coauthors applied the same treatment modalities being used on families to couples in crisis. "You look at the couple, instead of any one individual, or assigning blame," his daughter said.
In the early 1980s, Mr. Montalvo and ASPIRA's Manuel Gutiérrez wrote about the possible misuse of cultural identity when mental-health professionals treat minority families.
"In fact, by manipulating and restricting the therapist's attention to only certain aspects of their heritage, families can actually use their culture as a defense against change," the two wrote. "Client families can offer the therapist a cultural mask, a profile of who they presumably are, rather than show the essential ways they operate."
The challenge, the two wrote, was to get beyond the stereotypes.
Mr. Montalvo's last book was a collection of short stories, Hilachas, meaning threads, about his childhood in Puerto Rico.
In person, he was generous, opening his home to friends in need of a place to stay. He enjoyed arguing with his daughter about politics, seeing movies, and sending funny comic strips to friends.
He and his wife, the former Margarita Gonzales, spent many Albuquerque evenings dancing to salsa music or going out to concerts. The two were married for 54 years.
While in Philadelphia, he took his daughter to Phillies and 76ers games but passed on the Flyers. He acted as a sounding board for his daughter.
"There wasn't much I didn't talk to my dad about," she said.
Besides his wife and daughter, he is survived by a sister; a brother; and many nieces and nephews. A son, Carlos, and a brother died earlier.
Services were Saturday in Albuquerque.
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