In the suit against R.J. Reynolds, the Missouri Circuit Court certified a class of all persons who bought Camel Lights, Camel Special Lights, Salem Lights, and Winston Lights in Missouri from the date those cigarettes were first sold. In the suit against Altria, the court certified a class of all Missouri residents who purchased Marlboro Light cigarettes, beginning the date the cigarettes were first sold, but excluding those who have personal injury claims.

In the underlying lawsuits, the plaintiffs charged that the tobacco companies violated the Missouri Merchandising Practices Act by falsely representing that their light and low-tar cigarettes delivered less tar and nicotine to smokers than regular cigarettes. In addition, the plaintiffs claimed that the companies failed to inform their customers that the light and low-tar cigarettes were in some respects more dangerous to human health than regular cigarettes.

The plaintiffs argued in their petition that smokers receive the same dose of tar and nicotine from light and low-tar cigarettes as from regular cigarettes because of a universal phenomenon known as "compensation," in which smokers unconsciously adapt their smoking behavior. These behavioral adaptations include inhaling the smoke more deeply, holding it in for a longer period of time, and smoking more cigarettes.

In a study by the National Cancer Institute (NCI) titled “Risks Associated with Smoking Cigarettes with Low Machine-Measured Yields of Tar and Nicotine,” national scientific experts concluded that evidence does not indicate a benefit to public health from changes in cigarette design and manufacturing over the last 50 years. The report was made possible by the work and cooperation of scientists throughout the country. The monograph purportedly demonstrates that people who switch to low-tar or light cigarettes from regular cigarettes are likely to inhale the same amount of cancer-causing toxins and they remain at high risk for developing smoking-related cancers and other diseases. The monograph is the 13th volume in NCI's Smoking and Tobacco Control Monograph Series, which began in 1991.

The study describes several reasons why the levels of tar and nicotine measured by the FTC method do not reflect actual tar and nicotine delivery to the smoker. The filters in low-tar/low-nicotine cigarettes often include vent holes which, when open, allow air to enter and dilute the smoke. However, many smokers cover these holes with their lips and fingers. In contrast, when tested by a machine, the holes are unobstructed, and artificially low measurements of tar and nicotine are obtained.

Additionally, smokers who switch to light cigarettes from regular cigarettes do compensate for the lower nicotine level by inhaling more deeply, as alleged by the Missouri actions; taking larger, more rapid, or more frequent puffs; or by increasing the number of cigarettes smoked per day. As a result, smokers cancel out any potential benefit of smoking a "low-tar" cigarette.

The actions allege that the following brands of light cigarettes have all been inappropriately marketed:

Marlborough Lights
Camel Lights
Kool Lights
Merit Lights
Winston Lights
Salem Lights
Newport Lights
Now
Vantage
Carlton
Misty Lights
Capri Lights
Cambridge Lights
GPC Lights
Doral Lights
Virginia Slims Lights
Benson & Hedges Lights
Parliament Lights
Kent III Lights
Lucky Strikes Lights
True Lights