The painted green arrow on the ground starts in the parking lot, then leads inside one of Iran's largest family-planning clinics.
The arrow has already been worn down by the feet of 20,000 men seeking vasectomies. "It's so that clients can find us without asking, if they're embarrassed," says Fereydoun Forouhary, director of the clinic.
Though it is commonly believed in many Islamic societies that large families are good, Iran has taken a decidedly different approach. Its public embrace of family planning has been so determined that - as the global population officially surged to more than 6 billion last month - the United Nations considers Iran a model for Muslim nations worldwide.
"These mullahs are often seen as fundamentalist," says a longtime Iranian observer who asked not to be named. "But on family planning they have been very flexible, progressive, and pragmatic."
Iran's transformation has been one of extremes. During the early days of the Islamic revolution 20 years ago, babies were sought to bolster the ranks of "soldiers for Islam." By 1986, the population had jumped in a decade from 33 million to nearly 50 million. But when the Iran-Iraq war of the 1980s was over and Iran's economy took a significant downturn, the country faced serious challenges in supporting this number of people. Job shortages were particularly acute.
Presented with these facts, Ayatollah Ruhollah Khomeini - the Shiite Muslim spiritual leader who led the revolution - permitted debate on the subject of birth control.
"Our government was young, and we were involved in the war," says Dr. Forouhary about the early maximum-baby policy. "But when it was finished, we had time to think. Khomeini always spoke of being up to date, and he and [present spiritual leader Ayatollah Ali] Khamenei have issued fatwas [religious edicts]. They prefer the quality of life and not the quantity of the population."
The Koran, the Muslim holy book, makes no specific mention about birth control, though the Prophet Muhammad himself is recorded as saying, "Marry and multiply, for I shall make a display of you before other nations on the Day of Judgment."
Proponents of family planning counter, however, with these words of the prophet: "The most grueling trial is to have plenty of children with no adequate means." That view seems to have been accepted by many Islamic jurists, including the rector of Cairo's famous Al-Azhar University 35 years ago, who noted that greater numbers were required only in ancient days so that Islam would survive.
In Iran, Shiite Muslim jurisprudence provides for an especially flexible interpretation to fit aged verse with modern realities - and new choices.
"In the early day [Iran's ruling clerics] were out of touch," the Iranian observer says. "But then they realized it was too much. Now the clerics are politicians too, and running the country, so they must be in touch with day-to-day life."
Women still must wear the baggy chador and head scarf in public, according to religious rulings. And abortion is forbidden. But every form of contraception is encouraged and has religious sanction.
The result has been "unbelievable," as Iran's population growth rate has more than halved to less than 1.47 percent in a decade, says Mohamed Mosleh-Uddin, representative of the UN Population Fund (UNFPA) in Tehran. "No other country did such great work in such a short time."
To many, Iran's strategy amounts to a mini "revolution" in itself. "The rest of the developing world has taken 30 to 40 years to get this far, but in Iran there are a 'package' of reasons for their success," says Mr. Mosleh-Uddin. "These three actors have worked together: great religious support, political commitment, and a good health infrastructure. In no other country are all these elements there."
Mosleh-Uddin also cites as a factor Iran's education system, which has increased literacy from 47 percent in pre-revolution days to 85 percent today.
The family-planning program is actually a revitalization of a previous one begun in the 1970s under Shah Muhammad Reza Pahlavi. Today, government health centers - which in remote areas cater to villages of just 500 people - are stocked with an array of contraceptives. Every service and government-provided contraceptive is free - including sterilizing operations for men and women.
Bolstering Iran's large program is the UNFPA, which provides certain contraceptives and education and plans to spend $11 million in the next five years. The UN also arranges for delegates from around the world to travel here to observe the Islamic republic's efforts.
Yet on the streets of Tehran, recognition from the outside means little compared with the official encouragement to limit family size.
"If I have fewer children, it will be better for society and for myself," said Shaban Ali, who was among men who have lined up at Forouhary's Shahid Jaffary Polyclinic to limit their families.
Elsewhere in Tehran, Ghodsi Nasiri, a retired nurse, recalls one of her most memorable moments working in a local clinic. Late one night a car decked in wedding flowers stopped outside, and the new groom knocked on her door.
Ms. Nasiri gave the man a month's supply of the contraceptives he asked for and then offered some recommendations.
"His face was wide with such a smile of thanks," she said. "And then he tipped me!"
(c) Copyright 1999. The Christian Science Publishing Society