Household air pollution is a risk factor for pneumonia, the leading cause of death among children < 5 years of age. From 2008 to 2010, a Kenyan organization sold ≈ 2,500 ceramic cookstoves (upesi jiko) that produce less visible household smoke than 3-stone firepits. During a year-long observational study, we made 25 biweekly visits to 200 homes to determine stove use and observe signs of acute respiratory infection in children < 3 years of age. Reported stove use included 3-stone firepit only (81.8%), upesi jiko only (15.7%), and both (2.3%). Lower, but not statistically significant, percentages of children in upesi jiko-using households than 3-stone firepit-using households had observed cough (1.3% versus 2.9%, rate ratio [RR] 0.48, 95% confidence interval [CI]: 0.22-1.03), pneumonia (0.9% versus 1.7%, RR 0.60, 95% CI: 0.24-1.48), and severe pneumonia (0.3% versus 0.6%, RR 0.66, 95% CI: 0.17-2.62). Upesi jiko use did not result in significantly lower pneumonia rates. Further research on the health impact of improved cookstoves is warranted.