The first step after an investigator is called to investigate a fire is the preparation of a case-numbered notebook which constitutes the total information source for the investigation. The second step involves determining the following before probing the fire scene: (1) the investigator's legal grounds, (2) possession of appropriate 'tools of the trade,' (3) whether the fire scene has been protected, and (4) whether the investigator should report to the chief officer at the fire or at his quarters. The third step consists of obtaining relevant evidence outside and inside the burned building. Investigators should then review their findings and decide if further investigation is called for. Investigators should interview the owners of the business or building if they are at the scene, as soon as some evidence of arson is found. After having tagged and secured all physical evidence, investigators should conduct a door-to-door canvass of the area to obtain relevant information from residents of the area. The remaining steps include making one last tour of the fire scene, reviewing all of the evidence and information obtained, contacting the district attorney when arson is suspected, deciding whether to continue the investigation, and preparing witnesses for court. Twelve bibliographic entries are included.