The American Academy of Pediatrics recently removed nicotine from the list of drugs contraindicated during breastfeeding. The objective of this study was to evaluate the feasibility of determining the effect of a smoking hygiene intervention on infants of breastfeeding mothers who smoke cigarettes. An experimental design with repeated measures was used. A convenience sample of 35 mother-infant dyads from seven sites was recruited and randomly assigned to the intervention or control group. Of the 27 dyads completing the study, 16 were in the experimental group and 11 were in the control group. Smoking hygiene was introduced when infants were 2 weeks old and reinforced when they were 3 and 5 weeks old. At these three data points, infant health and urinary nicotine and cotinine levels were measured, as well as the mothers' breast-milk nicotine and cotinine levels and smoking hygiene behaviors. Recruiting and retaining a sample of breastfeeding mothers who smoke proved difficult. Only 27% of women in the intervention group implemented all aspects of the smoking hygiene intervention behaviors. Repeated-measures ANOVA revealed no difference in a) infant urinary nicotine and cotinine levels or b) breast-milk nicotine and cotinine levels between the two groups. The McNemar test for related samples revealed no difference between frequency of respiratory symptoms in either the control or intervention groups when Week 2 levels were compared with levels at Weeks 3 and 5. Mothers were not successful in adhering to the smoking hygiene intervention. To adequately test interventions, strategies must be developed to help women incorporate health-promoting behaviors into their lives.