In 1997 forward, respondents who had ever smoked 100 cigarettes (SMOKEV) and who were "Every day" smokers (IPUMS NHIS code 3 in SMOKFREQNOW) were asked, "On the average, how many cigarettes do you now smoke a day?" with responses recorded in CIGSDAY1. Respondents who had ever smoked 100 cigarettes (SMOKEV), who were "Some day" smokers (IHIS code 2 in SMOKFREQNOW), and who smoked 1+ days or an unknown number of days during the past 30 days (according to CIGDAYMO) were asked, "On the average, when you smoked during the past 30 days, about how many cigarettes did you smoke a day?" Responses to this question are reported in CIGSDAY2. The variable CIGSDAY combines responses given to the questions associated with CIGSDAY1 and CIGSDAY2, reporting the average number of cigarettes smoked per day for "current smokers" (i.e., all "every day" smokers and "some day" smokers who smoked 1+ days or an unknown number of days in the past 30 days). The universe for CIGSDAY also includes (in 1997-2003) respondents whose current smoking status was unknown (IHIS code 7-9 in SMOKFREQNOW). Respondents whose smoking status was unknown were all coded as "Unknown-not ascertained" in CIGSDAY (IHIS code 98).

The 1970 Field Representative's Manual instructed interviewers to "[e]xclude marijuana, a type of wild tobacco, (also called "pot" or "grass')" when accepting responses to the question associated with CIGSDAY.

The question for CIGSDAY 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 not in universe for this variable. Users may choose to use this variable in combination with SUBSRESP77, which reports the person's sub-sample status in 1977.

The 1997-2000 Field Representative's Manuals stated, "The questions in this section concern cigarette smoking only. Accept whatever the Sample Adult reports, except if it is volunteered that he/she smoked a pipe, cigars of any kind, marijuana, hashish, 'crack', or the like." The Manuals for 2001 forward define a cigarette as "anything the respondent reports except cigars or any kind of marijuana."

The 1970 Field Representative's Manual instructed interviewers, "If the response is expressed in 'pack(s)' smoked per day, convert this to the number of individual cigarettes smoked (20 to a pack). For example, if a person reports 'About a pack and a half a day,' enter '30' for the number smoked per day." The Manuals for 1976-1977 and 1997-2000 included similar instructions. The 1997-2000 Manuals added, "verify the result with the Sample Adult (some brands have 25 cigarettes per pack)."

The 1970 Manual also included the following instructions:

When asking the question associated with CIGSDAY1 or CIGSDAY2, the 1997-2000 Field Representative's Manuals instructed interviewers to "[a]lways probe for an exact number" and to assist respondents in making an estimate if they reported a range or interval. For the question associated with CIGSDAY2 (Number of cigarettes smoked per day: Some day smokers), the 1997-2000 Manuals instructed interviewers, "Do NOT include days when the Sample Adult did NOT smoke in computing the average."