Space in the city's 103 public cemeteries is so tight that since 1975, the law has required family members to dig up bodies after as few as seven years to make room for the more recently departed. An estimated 1.4 million sets of remains occupy such temporary graves in Mexico City.
"Family members want their loved ones to rest in peace, to have their own grave where they can sleep without being disturbed," said Pablo Rocha, director of the Dolores public cemetery.
"But in Mexico City that's almost impossible. Too many people lived here and died before the rest of us came along."
Things are so cramped that a market has sprung up in which families willing to evict their loved ones can get thousands of dollars for the space, and city officials have taken to touting the advantages of cremation in radio ads.
Under city regulations, after seven years cemetery officials dig up and cremate the remains. Family members can buy postponements totaling an extra 14 years, but after that all post-1975 public tombs have to be excavated.
"We have to be practical. There is no longer room for emotion," said Raul Escobar, head of the city's funeral-services department.
Families that control older plots have begun to add bodies to graves built for one person, rather than put them in a new tomb with a time limit.
When families want to add a body to an older, permanent plot, gravediggers exhume remains and let relatives choose either to cremate them or put what's left of the corpse in a small box that is attached to the top of the new coffin.
Eternal rest can still be bought at 15 private cemeteries in the city, but these charge up to $5,500 for a burial service, compared with less than $5 at a public graveyard.
The Dolores cemetery is among Latin America's largest. Opened in 1876 and ringed by a park that shuts out the noise of the city, its 600 acres are crammed with 375,000 individual and family grave sites holding more than 1 million sets of remains, including those of painter Diego Rivera and three Mexican presidents.
The Dolores cemetery hasn't had a vacancy for graves since 1970 but employs a small army of gravediggers to handle an average of 10 excavations a day.
The cemetery crunch gives Gloria Rica an additional reason to hope that her ailing mother doesn't die before 2005, the seventh anniversary of her father's death.
If she goes before that, the family won't be able to exhume the father to make room for the mother because health regulations require that a corpse stay buried for at least seven years.
Grocery manager Freddy Escobar, 41, said a neighbor offered him $2,200 for his family's permanent plot in the jam-packed La Via cemetery on Mexico City's north side. The waist-high brick crypt holds the remains of his brother, father and grandparents. Escobar declined.
"If I sold it, the rest of my family would have nowhere to rest," he said.
Among rows of headstones so close together that visitors have to climb over them when walking through La Via, it's not uncommon to find a gaping hole and a collection of human bones where a grave is being excavated. Families must pay for the upkeep of graves, and those that are neglected, including pre-1975 ones, are emptied and their contents cremated. The city has built seven public mausoleums to house their ashes.
Like many city people, Mario Ornesto buried his father in a suburban cemetery, where the seven-year rule doesn't apply.
"A man deserves to be buried in the place where he lived his life, but I think he would prefer not to be moved," said Ornesto, an out-of-work electrician. "Now after seven years, my family will have only memories of him, not worries about an excavation."
Escobar said four new public cemeteries are planned over the next six years, but the extra space won't meet demand in a city of 20 million where nearly 200 corpses are brought to public cemeteries every day.
Ornesto said the restrictions already are too much for him.
"When I die I'm going to be cremated," he said. "You can put your ashes anywhere, and nobody comes to you in seven years and says, 'Hey, we need that space.' "