Data on daily work-output (kg of leaves plucked) of Oraon pluckers in tea gardens of Jalpaiguri district, West Bengal, India, are analysed. While on any particular day of the week there is no significant difference in work-output of males and females, there is a significant between-day variation in work-output for both sexes. Mean work-output steadily decreases as the week progresses, perhaps due to the cumulative effect of fatigue.

The relationship between hepatitis B infection in parents and the sex ratio at birth of their offspring is examined in four populations. The hepatitis B carrier state in parents may increase the sex ratio of their offspring, but it seems that immunization against hepatitis B is unlikely to affect the sex ratio at birth of future generations.

An analysis of the 1980 Uganda Population Census for South Kampala through indirect techniques provided estimated 1q0 values of 0·0860, 0·0680 and 0·0774 for male infants, female infants and both sexes respectively. The estimated level of 4q1 is 0·0491. The level of adult mortality, especially from age 5 to 19, is lower than infant and child mortality. There is a clear evidence of a sex differential in mortality, males experiencing higher mortality than females. Estimates of expectation of life at birth provided further evidence of sex differences in mortality. The estimated life expectation for males is 54·7 years, for females 59·3 years, and for both sexes 57·0 years.

The distribution of consanguineous marriages among spouses and husband's and wife's parents, was analysed using data on 9225 families in six widely different areas of Japan. With two exceptions, the consanguinity rates for husband's and wife's parents are higher in related spouses than in unrelated spouses. The familial aggregation of consanguinity was slightly decreased in more recent marriages, a change which began recently with couples who have abandoned the more traditional Japanese way of life.

Data from a survey of 3727 14-year-old children from 31 secondary schools in England in 1984–85 were analysed to obtain information about smoking habits, bedtimes and times of rising in the morning, on a weekday during school term. Subjects completed a questionnaire, anonymously, in class. Twenty percent of respondents reported that they currently smoked cigarettes. Smokers went to bed significantly later, and spent significantly less time in bed, than non-smokers. Twice as many smokers as non-smokers went to bed at or after 22.30, went to bed after midnight, and spent 7·5 hr or less in bed. Possibly, some adolescent smokers may be at risk from loss of sleep.

The relationship between female labour force participation, and other socioeconomic factors, and the probability of having a third birth is examined, using British data collected in the 1980 Women and Employment Survey, by hazard regression modelling with time-varying covariates. The results demonstrate the strong association between demographic factors, e.g. age at first birth and birth interval and subsequent fertility behaviour. Education appears to have little effect. Surprisingly, women who have spent a higher proportion of time as housewives have a lower risk of having a third birth. This finding is in sharp disagreement with the conventional expectation that cumulative labour force participation supports lower fertility. These findings are briefly compared with similar research carried out in Sweden.

In a cross-sectional study of gallstone disease, ascertained by ultrasonography, the prevalence was assessed in relation to clinically diagnosed gallstones in first degree relatives by selected socioeconomic factors. In both sexes, clinically diagnosed gallstones among first degree relatives occurred significantly more frequently among subjects with than among those without gallstone disease. None of the socioeconomic variables was significantly associated with gallstone disease in females. In males gallstone disease was positively associated with longer school education, living alone, and duration of residence in the municipality of Copenhagen.

There is no agreed explanation of the social class gradient in infant mortality. The longstanding debate continues between those who favour explanations based on natural or social selection and those who stress the influence of environmental circumstances. These explanations are often presented as competing hypotheses between which it is necessary to make an absolute choice. An article which takes this approach is critically examined. It is argued that such an approach may lead to erroneous conclusions, and may divert attention away from the primary task of understanding how to bring about further improvements in the survival of infants in the manual social classes.