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Vital statistics data on mortality from malignant melanoma from five countries are simultaneously fit by the method of cohort analysis. After the effects of geographic and temporal trends are removed, the proportion of deaths occurring in the younger age groups is found to be higher in females than in males. Relative increases in mortality rates by birth cohort are approximately equal in different regions and appear to be slowing down in recent years.

Three parametric families of relative risk functions for the analysis of case-control data are discussed. A desirable feature for any general relative risk function is that inference based on it be independent of the coding of a binary covariate. Only one of the three families considered has this property. Additionally, when the relative risk is not multiplicative, methods of inference based on the asymptotic covariance matrix are likely to be seriously misleading unless the sample size is very large, as has been noted previously in other papers. This is illustrated by means of examples. Likelihood-based procedures should routinely be employed when nonmultiplicative relative risk functions are used for analysis of case-control data.

A programme of iodized oil injections was carried out in an area of high goitre prevalence (28.5%) in rural Zaire. The iodized oil programme was undertaken as a part of a broader, pre-existing community health programme. No complications were encountered.