We developed a microarrayer system for the manufacture of DNA chips. The 3-axis robot was designed to automatically collect samples from 96- or 384-well microtiter plates using up to 16 pens simultaneously and deposit them on a modified glass slides. This is followed by a wash/dry operation and the cycle is repeated with a new set of samples. This system can deposit cDNA with an interval of 150 micrometer to 80 micrometer in size, thus allowing high-density DNA chips of about 5,000 ea/cm2 to be made. An in-house Visual C++ program running on a Pentium computer controls the whole procedure. With our DNA chip microarrayer, we made DNA chips containing a set of genes whose products are involved in the primary metabolic pathways, heat shock response and protein secretion in Escherichia coli. Expression of these genes in Escherichia coli was monitored under various conditions: recombinant protein production, high-density cell culture, etc. Details of the step-by-step procedures for manufacturing DNA microarrayer and DNA chips will be presented. Also, the results from the expression monitoring of central Escherichia coli genes under various cultivation conditions will be presented.