We see from the range of conditions that speech and language therapists assess and diagnose that they must possess wide knowledge in the fields of:
Generalist speech and language therapist
Typically, a speech and language therapist (speech-language pathologist)  starts her or his speech and language therapy career as a generalist therapist, gaining experience in assessing, diagnosing and intervening across the full range of communication disorders (and, in some cases, swallowing disorders).
Over time, and with more experience, many speech and language therapists choose to specialize in an area of work. For example:
- Some speech therapists choose to specialize in working with a particular age group: e.g. working with elderly persons (geriatrics); adults; children and young people.
- Others take up speech pathology jobs that allow specialization in particular conditions irrespective of the age of the client or the presenting communication disorder, e.g. neurological impairment; physical impairment.
- Still others may choose to work solely with particular communication disorders such as voice disorders, speech disorders or stuttering (irrespective of the age of the client or the underlying impairment which may have caused the particular communication difficulty).
- Specializing in the general field of rehabilitation.
- Pursuing research.
Specialist speech and language therapist job
The above list is only an example of some of the specialism routes available: the possibilities for specialization are extensive. Which specialisms are available in any geographical area will depend on many factors, including:
- the health profile of the local population
- whether the service takes referrals from other parts of the country (or from abroad)
- the budget available
By way of example, a Speech and Language Therapy Department that I managed for several years, and which served a population of around 120,000 people, included the following specialist posts :
- Specialist Speech and Language Therapist in Pediatric Special Needs
- Specialist Speech and Language Therapist in Hearing Impairment
- Specialist Speech and Language Therapist in Alternative and Augmentative Communication Aids
- Specialist Speech and Language Therapist in Pediatric Stuttering
- Specialist Speech and Language Therapist in Voice
- Specialist Speech and Language Therapist in Mainstream Pediatrics
- Specialist Speech and Language Therapist in Dysphagia
Specialist speech and language therapists will have undertaken additional specialized training courses to support their increased expertise and their focus on a particular age group, condition, or communication disorder. For example, a speech and language therapist who specializes in working with people with cleft palate will most likely need to undertake additional training in phonetic transcription, i.e. a notation system for writing down an accurate representation of the sounds a person makes when speaking. All speech and language therapists can carry out so-called phonemic transcription but people with cleft palate often produce non-standard sounds and additional notational symbols need to be learnt to represent these in writing. Similarly, a speech and language therapist who specializes in swallowing difficulties (dysphagia) will need to undertake additional post qualification training in assessing, diagnosing and treating eating and swallowing difficulties. Anyone specializing in research will need to undertake post-graduate training in research methods.
 Qualified practitioners around the world use different (authorized) titles, e.g. speech-pathologist (Australia); logopedist (Italy).
 In the UK, specialist speech and language therapists working in the National Health Service (NHS) are usually called Highly Specialist Speech and Language Therapists.