BACKGROUND We report the first case of occupational asthma due to gluteraldehyde exposure in Singapore and also describe the use of a specific inhalational challenge (SIC) test in confirming the diagnosis. METHODS A 32-year-old laboratory technician presented with adult-onset asthma 2 years after daily exposure to gluteraldehyde which was used to sterilise the mouthpieces used for lung function testing. SIC testing showed a 25% drop in FEV1 after exposure to gluteraldehyde but not after exposure to a control, thus confirming the diagnosis. METHODS Alternative arrangements were made for sterilisation of the mouthpieces so that gluteraldehyde could be removed from the workplace. There was a marked improvement in her asthmatic control thereafter. CONCLUSIONS This case illustrates the use of a SIC test in the diagnosis of occupational asthma. Gluteraldehyde is a known cause of occupational asthma and should be kept in mind when evaluating asthmatic patients in at-risk occupations. Effective ventilation and proper storage should be ensured to minimise exposure to gluteraldehyde where its use is necessary.