Background:
Many studies have shown that pictorial health warnings (PHWs) are more effective in increasing knowledge about the many harms of cigarettes. Zambia currently has a single text-only English warning covering less than 3% of pack. This study is the first to assess health knowledge and the effectiveness of warnings in Zambia.

Methods:
Data were from 1,171 smokers in the International Tobacco Control (ITC) Zambia Wave 2 Survey (2014), a longitudinal survey of a nationally representative sample of Zambian adults. Key variables analyzed were knowledge of specific harms of smoking and validated indicators of warning effectiveness.

Results:
Knowledge among Zambian smokers was very low compared to other ITC countries: only 45% knew that smoking causes stroke (2^nd lowest among 20 ITC countries), heart disease (74%--3^rd lowest among 14 ITC countries), and lung cancer (79%--lowest among 12 ITC countries). The Zambian text-only warning was very ineffective: 58% of Zambian smokers reported “never” or “hardly ever” noticing the warning; only 24% reported closely reading the warning. 75% reported that warning “never” stopped them from smoking; 70% reported that warning did not make them more likely to think about health risks; 66% reported that warning “never” made them think about quitting. When shown the warning, 55% of smokers were not able to easily read it. And yet 71% thought the packs should have more health information and 86% wanted the government to do more about harms of tobacco use.

Conclusions:
Knowledge of tobacco-related harms is very poor among Zambian smokers and the single-text only warning provides no help, particularly among the many low literacy smokers in Zambia. There is a clear need for Zambia to implement pictorial health warnings, as they are obligated to do as a Party to the FCTC and as other African countries - Mauritius and Kenya - have already done successfully.