Cryptographic systems are systems of secret writings typically undertaken by criminals to conceal their activities. Two major categories of cryptographic systems are codes and ciphers. The author begins by describing cipher systems, which involve the replacement of true letters or numbers with different characters or the systematic rearrangement of the true letters without changing their identities to form an enciphered message. Different types of cipher systems and instructions for how to solve them are described, including simple substitution ciphers, keyword number ciphers, and telephone keypad ciphers. Next, code systems are described, which are created by replacing individual characters of plain text with cipher text characters. Code systems are different from cipher systems because code text may represent letters, numbers, words, or phrases. Codes are generally used for secrecy and brevity. Different types of codes and instructions on how to solve them are described, including sports bookmaking codes, horse race bookmaking codes, and numbers bookmaking codes. While the ciphers and codes described here are relatively easy to decipher, many are not and require the expertise of the Racketeering Records Analysis Unit (RRAU) of the FBI’s Laboratory, who have training in cryptanalysis, drug trafficking, money laundering, and racketeering activities. Contact information for the RRAU is provided along with a description of some of the services they provide, such as pretrial advice and assistance and on-site examinations and consultations.