Breast milk from 10 women each from the city of Hamburg and from a rural area was analyzed by atomic absorption spectrometry for contamination with lead and cadmium. Samples were examined at regular intervals for 3 months after birth. On day 5 a diurnal profile was analyzed; on the other days milk was taken before and after the morning feed. Daily permissible intake (DPI) for lead is 5 micrograms/kg/day for children; the DPI for cadmium has as yet been determined only for adults as 400-500 micrograms/week, equivalent to about 1 microgram/kg/day (WHO 1972). For breast milk as the main source of nutrition in infants, this study shows values of 9.1 +/- 2.5 (SD) microgram/l for lead in the rural population, with a tendency to decrease towards the end of lactation. Urban mothers had 13.3 +/- 5.5 (SD) microgram/l, with a tendency to increase. This difference was significant only on day 45. Mean cadmium content in rural mothers was 17.3 +/- 4.9 micrograms/l, with much higher values in the colostrum and a decrease after 15 days. Urban mothers had 24.6 +/- 7.3 micrograms/l, again with high colostrum values and a subsequent decrease. These latter values are not significantly different. Calculated daily intake according to these values is presented, based on 840 ml breast milk for a 5.5 kg infant per day. Rural infants ingested 0.9-1.3 micrograms/kg/day of lead, and in the city 1.5-2.3 micrograms/kg/day. Cadmium intake in rural infants amounted from 1.2-1.8 micrograms/kg/day; in Hamburg it was 1.6-2.2 micrograms/kg/day.(ABSTRACT TRUNCATED AT 250 WORDS)