For surveys in the years 1970 through 1991, the basic cigarette smoking status questions consisted of two parts: (1) "Have you smoked at least 100 cigarettes during your entire life?" If yes, "Do you smoke cigarettes now?"

The question for SMOKESTATUS1 in 1977 was asked for a sub-sample of randomly selected persons age 20 and over; NHIS automatically classifies persons who were selected but did not complete the questions as responding "unknown " for this variable. Users may choose to use this variable in combination with SUBSRESP77, which reports the person's sub-sample status in 1977.

For all years, a person was considered to have never smoked or was a nonsmoker if he did not smoke more than 100 cigarettes during his entire life. Respondents who ever smoked more than 100 cigarettes in their entire lives were classified as "ever smokers" and were further categorized into current or former smokers. Current smokers were those who reported smoking from less than one cigarette per day to 99 or more cigarettes per day. A former smoker was anyone who has smoked at least 100 cigarettes during his entire life did not smoke at the time of the interview.

For 1985 and 1990, the term "regular smoker" was respondent defined (Interviewers were instructed to "accept the respondent's interpretation of "fairly regularly.")

In 1991, current smokers were divided into "everyday" smokers or "someday" smokers). That year, the NHIS started to distinguished smokers who smoked daily from those who smoked less often than daily. Those who said "no" to the current smoking status question, were asked, "Do you smoke some days or not at all?" This additional follow-up resulted in the classification of persons as "someday smokers" who would otherwise have been considered former smokers, since they initially said that they did not smoke now. From 1991 forward, someday smokers, as well as everyday smokers were categorized as "current smokers."

In 1992, questions on smoking status were included in two parts of the survey to allow for estimation of the effect of changes in question wording. Cancer Control section contained the same three questions as in the 1991 questionnaire, while the Cancer Epidemiology questionnaire used just two questions: "Have you smoked at least 100 cigarettes during your entire life?" If yes, "Do you NOW smoke cigarettes every day, some days, or not at all?" This version of the question was used from 1992 forward.

These include:

• SMOKESTATUS2 which categorizes respondents into current smoker, every day current smoker, some day current smoker, current smoker--unknown frequency of smoking also indicates former smoker, never smoked and "has smoked, current smoking status unknown."

• SMOKESTATUS3 categorizes respondents into current every day smoker, current some day smoker ((1 or more days, past month), current some day smoker (0 days, past month), current some day smoker (unknown days in past month) and also indicates former smoker, never smoked and "has smoked, current smoking status unknown."