The flavour enhancer, monosodium glutamate (MSG) was first implicated in causing adverse reactions in 1968, when Dr. Kwok wrote a letter to the New England Journal of Medicine explaining how he felt after eating in a Chinese restaurant. A possible association between MSG and asthma was also first proposed in a letter, to the New England Journal of Medicine, from Alien & Baker in 1981. Since this time six clinical trials, to determine the relationship between MSG and asthma, have been conducted throughout the world and published. Two of these trials have shown an association between MSG and asthma (14 of 62 subjects were defined as having MSG-induced asthma in one study, and 2 of 30 in the other). However four trials, involving 45 subjects with a positive history of MSG-induced asthma, have shown no such association. A further trial, which assessed a range of food chemicals in adults with asthma, demonstrated MSG-induced asthma in one out of the eight subjects studied. Attempts to clarify this issue have been limited due to methodological deficiencies, including the small number of subjects studied, inadequate blinding procedures, inappropriate withdrawal of asthma medications, poor dietary control and the use of effort-dependent measures of lung function. Recent reviews of the relationship between MSG and asthma have concluded that a causal connection between MSG and asthma has not been conclusively established.