This report is a detailed description and analysis of the methods, problems, and results of mental testing carried out in the home as a phase of a community survey of mental retardation. A group of 409 individuals were tested, including a random sample of persons scoring in the lowest 10% of the developmental scales completed by the initial interviewers and a random sample of all persons in the interviewed households. Little testing of this type has been done in most other surveys of this nature; still fewer studies attempted testing in the home itself. The descriptive information on this successful project should be of value to other investigators who are interested in developing community-wide surveys.