A urologist at Sinai Hospital and Greater Baltimore Medical Center, Dr. Edward Leventhal would be hard-pressed to squeeze in Jewish education classes between performing surgeries.

Instead, the Owings Mills resident logged on to www.jewishstudies.org, joining thousands of professional Jews who depend on the non-profit Jewish educational service as a source of Jewish education.

"This allowed me the ability to study at 5 a.m. or 11 at night," said Dr. Leventhal, 39, raised in what he described as a non-practicing Conservative home. "I could study at my leisure. ... Especially when you're a busy surgeon, you don't have time to take courses at Baltimore Hebrew [University]."

Jewish Interactive Studies was developed three years ago by Rabbi Moshe Zauderer, an accountant who earned a bachelor's degree in talmudic studies from Pikesville's Ner Israel Rabbinical College, where he studied from 1983-1988.

JIS does not offer quick-read nuggets of Jewish inspiration, such as those available on other Jewish Web sites. Classes, modeled after online college courses that have gained popularity in recent years, can take more than a half-hour to read. About 55 Marylanders participate in JIS, 16 of whom are Baltimore residents.

Courses explore topics including the foundations of Judaism, the Bible, Jewish holidays and ethics. Sample classes, detailed syllabi and registration forms are available through the Web site.

"We're giving [interested Jews] the opportunity to learn in-depth, classical Jewish sources on a variety of topics," said Rabbi Zauderer, JIS director and author of its 12 courses.

During his annual trip to Baltimore last week, Rabbi Zauderer, 37, lectured at Congregation Tiferes Yisroel in Park Heights. In the past year, Rabbi Zauderer began lecturing internationally about using classical Jewish sources to answer modern questions.

According to Rabbi Zauderer, JIS differs from other Jewish Web sites that offer online courses because it "offers direct access to classical Jewish texts. People can see for themselves what Maimonides and Rav Sa'adiah Gaon have to say about Judaism."

JIS is a program of Zichron Avos (Memorial to the Forefathers) — Jewish Interactive Studies Foundation. The non-profit foundation, based in Philadelphia, was founded by Dr. Bert Zauderer (Rabbi Zauderer's father) in memory of family members killed during the Holocaust. JIS's annual $100,000 budget is funded through private donations.

Students read each class, which is posted online for one week, and can e-mail questions to Rabbi Zauderer. Some, such as Dr. Leventhal, instead choose to read the material without responding to questions or posing their own.

"We want to make it clear to people, so it's not like wading through the original material," he said. "Judaism has such a wealth of classical literature that can be accessed if one has the tools to do it."

Three courses, four to nine weeks each, are offered during each of the year's four semesters. Classes can only be accessed by students registered for a course, though registration is free.

JIS differs from traditional college courses in that there are no requirements and courses are free. Students who complete courses do not receive a degree, certificate or credits.

A Philadelphia native, Rabbi Zauderer oversees the online courses from his home in Jerusalem, where he has lived since 1988. He and his wife, Shira, have five daughters. He is the author of "Abraham: Lessons For Our Time," published last year by the Zichron Avos foundation.

Approximately 2,000 Jewish adults have participated in JIS since its inception. And while the majority of JIS students are from the United States or Canada, JIS also attracts participants from places including Europe and Asia.

JIS courses tend to attract professionals — including educators, lawyers and engineers — between the ages of 25 and 59. Eighty-two percent describe themselves as having little or no Jewish education.

According to Rabbi Zauderer, the typical Jew participating in JIS is either too busy to attend Jewish courses or lives outside of communities in which such courses are offered.

While JIS is geared toward those with little Jewish background, it is also useful to those with an advanced Jewish education, he said. More than 10 percent of course participants are teachers using JIS material to develop a curriculum, he said.