Following his retirement from the Public Health Service, Kolb served as a consultant to the State of California Department of Corrections for a year, and then served as Deputy Director of the California Department of Mental Hygiene until 1951. His duties were part of a general post-war movement to reform existing mental health facilities and expand availability of treatment. He evaluated the state's mental hospitals and other facilities, revised criteria and exams for the department's personnel, and participated in the search for a new director in 1949. From mid-1951 to late 1952 Kolb was Assistant Superintendent at the Norristown State Hospital in Pennsylvania. While there he was asked to serve as secretary for the Philadelphia Mental Health Survey through 1954. This work, like the California State job, involved visiting and evaluating state and county facilities that treated mental disorders. From 1954, Kolb also held a consulting post at the National Institutes of Health.

In 1958, he participated in a NIH symposium on the historical aspects of addictive drug use, where he was recognized as "the Osler of addiction" and received a commendation for his pioneering work in addiction medicine, psychiatry, and public health. Kolb also devoted several years of his retirement to writing a book that included some of his most important work on drug addiction with perspectives gained from his many years with the PHS. Drug Addiction: A Medical Problem was published in 1962. He was pleased when federal addiction policies began to shift during the 1960s, providing a wider range of options for addicts, including methadone maintenance programs.

In his many years with the Public Health Service, Lawrence Kolb developed and applied new ideas in psychiatry to a variety of large institutions and populations: the mental testing of immigrants, the care of shell-shocked veterans, the care of severely ill prisoners, and the care and rehabilitation of drug addicts. As a physician, researcher, and administrator he made essential contributions to the theory and practice of psychiatry in these environments, often while negotiating the fundamental tensions between federal public health and enforcement bureaucracies. And his prescient proposal for a national mental health research institute ensured that federal support of all aspects of mental health, including drug addiction research and treatment, would be part of the post-war public health expansion at NIH. His consistent advocacy of medical approaches to drug addiction treatment during an era of harsh drug law enforcement supported the development of better treatment practices in the decades after his retirement.

In his obituary of Kolb, Robert H. Felix, first director of NIMH, recalled not just his accomplishments but his exceptional character: "A recital of the career of this remarkable man cannot communicate the warmly human side of his character or his vision, leadership, keen insight, and dedication to improving the lot of the mentally ill. Quietly forceful, he was an excellent organizer and administrator who inspired not only loyalty and respect but deep affection in his subordinates. He watched over and brought to professional maturity most of the career psychiatrists in the U. S. Public Health Service who occupied key positions during the early days of the national mental health program. While he was Chief of the Mental Hygiene Division, he blazed the trail that made possible the passage of the National Mental Health Act some years later. There would be no national mental health program as we know it today had it not been for his pioneering efforts." (Am. J. Psych. 130 (June 1973): 718-719.)