cDNA expression microarrays are becoming popular tools for high throughput expression profiling. To simplify use of the microarrays in research lab, we developed a disposable plastic chamber, which can be used for a hybridization assay with a single slide. We compare performance of the hybridization assay using conventional glass slide-cover slide with 50 µl of hybridization mix and hybridization chamber with 1 ml of hybridization solution. We have developed a procedure for generating highly sensitive fluorescently labeled cDNA probes. Low complexity hybridization probes were generated from poly(A)+RNA using mixture of gene-specific primers. Using allylamino-modified dUTP allows one to generate the cDNA containing primary amino groups, which can be efficiently coupled with Cy3 or Cy5 succinimid ester. Under the optimal hybridization buffer composition, both approaches give similar sensitivity. The hybridization chamber approach does not require any specialized equipment and can be used in any research lab.