Assortative marriage for smoking habits was studied in 68 engaged couples, 112 newly wed couples, and 223 couples married for six years or more. All three groups showed a fairly strong correlation between couples for smoking, r = 0.332 +/- 0.047 (mean + SD). Smoking habits were highly intercorrelated with social class and education but the correlation for smoking remained highly significant, even when correction was made for these factors. Because this correlation was present even in those who have not yet married, smoking habits may well be an important factor in choosing a marriage partner