Is Lazard Ltd. (NYSE: LAZ) CEO Bruce Wasserstein seriously ill? That's the word I'm hearing from the clubby world of Wall Street.

Wasserstein is arguably the leading investment banker of his generation. A graduate of Harvard's law and business schools, Wasserstein rose to prominence during the 1980s as part of a dynamic duo of M&A bankers at First Boston -- where he earned the moniker "Bid-em-up Bruce" for his aggressive negotiating style. In 1988 Wasserstein co-founded Wasserstein Perella & Co. with his First Boston partner, Joe Perella, which they sold to Germany's Dresdner Bank for $1.37 billion in 2000. He joined Lazard with the title Head of Lazard in 2002. His challenge was to take the 157 year old partnership public -- which he met in May 2005. Since then, Lazard's stock has risen 50%.

According to my source, a few weeks after the tragic death of his beloved sister Wendy, from lymphoma, and just after delivering his infamous report on Time Warner Inc. (NYSE: TWX), Bruce went into hiding for some eight weeks. He has lost 50 pounds and is said to look like a wobbly, 75-year-old. Bruce is 58 and has always been portly. He is apparently now back at work at Lazard and is to give a speech today.

This raises a significant question in my mind regarding a public company's obligation to disclose to investors a CEO's illness.

And it's not the first time that a CEO's health issues have taken investors by surprise. In June, Frank Lanza, CEO of L-3 Communications Holdings (NYSE: LLL) died of esophageal cancer after what had been described two months earlier as an operation to combat acid reflux disease.

Did L-3 know that Lanza suffered from cancer two months before his death? If so, what was L-3's obligation to disclose to shareholders its CEO's health condition?

Evidently there is no clear legal guidance. In my discussions with a lawyer, it appears that there are two conflicting points of view on the topic. On the one hand, the illness of the CEO -- particularly one as highly regarded as Wasserstein -- is material information under Regulation Fair Disclosure (FD) that could cause an investor to sell if it was disclosed. On the other hand, laws such as The Health Insurance Portability Act (HIPAA) protect the privacy of employee medical records.

I'm not a securities lawyer but it seems to me that an officer of a public company owes a duty to shareholders that supersedes that officer's privacy interest. So if the rumor of Wasserstein's illness is true Lazard should let shareholders know about it.

Peter Cohan is President of Peter S. Cohan & Associates, a management consulting and venture capital firm, and a Professor of Management at Babson College. He has no financial interest in the securities of Lazard, L-3 or Time Warner.